Dry composition for use in haemostasis and wound healing

ABSTRACT

The present disclosure relates to a dry composition which reconstitutes without mechanical mixing to form a flowable paste having a soft and light consistency suitable for use in haemostasis and wound healing procedures upon addition of an aqueous medium. The disclosure further relates to methods of preparing the dry composition, methods for reconstituting the dry composition and medical use of the composition.

This application is the U.S. National Stage of International Application No. PCT/DK2015/050311, filed Oct. 13, 2015, which designates the U.S., published in English, and claims priority under 35 U.S.C. §§ 119 or 365(c) to Denmark Application No. PA 2014 70634, filed Oct. 13, 2014 and Denmark Application No. PA 2015 70450, filed Jul. 7, 2015. The entire teachings of the above applications are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a method for preparing a dry composition suitable for use in haemostasis and wound healing procedures. The dry composition reconstitutes efficiently to form a paste having a soft, light consistency upon addition of an aqueous medium without mechanically mixing air into the paste.

BACKGROUND

Protein-based haemostatic materials such as collagen and gelatine are commercially available in solid sponge and loose or unpacked powder form for use in surgical procedures. Mixing of the loose or unpacked powder with a fluid such as saline or a thrombin solution may form a paste or slurry that is useful as a haemostatic composition for use in cases of diffuse bleeding, particularly from uneven surfaces or hard to reach areas, depending on mixing conditions and relative ratios of the materials.

Conventional haemostatic pastes are usually prepared at the point of use by mechanical agitation and mixing of a biocompatible polymer, e.g. gelatine, and a liquid, e.g. a thrombin solution, to provide uniformity of the composition. Mixing to form a paste usually requires extensive mixing, such as kneading or transfer between two syringes.

WO 03/055531 relates to a container comprising a fixed amount of haemostatic agent in powder form, such as gelatine powder. Upon addition of a suitable amount of liquid, mechanical mixing within the container may be performed by closing the lid and shaking the container. The resultant putty-like haemostatic paste can then be removed from the container and applied to a patient to promote haemostasis.

Surgiflo® Haemostatic Matrix (Ethicon) is a kit for producing a haemostatic gelatine paste comprising thrombin, which is prepared by transferring a gelatin matrix-thrombin solution mixture back and forth between two connected syringes for a total of at least six passes. Floseal® Haemostatic Matrix (Baxter) is likewise a kit for producing a haemostatic gelatine paste, but requires transfer of the gelatin matrix-thrombin solution mixture back and forth between two connected syringes for a total of at least twenty passes. Once a substantially homogenous paste composition is achieved, the haemostatic pastes can be applied to a bleeding to promote haemostasis by extruding the pastes from the syringe.

US 2005/0284809 relates to a method for preparing a haemostatic paste that more readily absorbs aqueous liquids, such that less mechanical force and time is required in order to form a flowable haemostatic paste. The paste of US 2005/0284809 is prepared from compressed haemostatic powder particles and to prepare the paste, it must be transferred back and forth between connected syringes for a total of at least five passes.

WO 2011/151400 relates to a process for making a dry haemostatic composition comprising a coagulation inducing agent such as thrombin and a biocompatible polymer such as gelatine. The coagulation inducing agent and the biocompatible polymer are mixed to form a paste and the paste is subjected to lyophilisation. The resulting dry composition is reconstituted by transferring the composition and a diluent back and forth between two connected syringes for a total of at least twenty passes as described previously.

Transfer between connected syringes ensures sufficient mixing of the liquid component and the gelatin matrix component. During the passes air is mixed into the paste, which affects the consistency of the reconstituted paste. However, mixing procedures and manipulations are time consuming which in an Operation Room (OR) setting with bleedings is not acceptable as the surgeon will have to abrupt his procedure while waiting for the haemostat. Mixing may also potentially compromise the sterility of the haemostatic paste and can in some cases even negatively affect the consistency of the haemostatic paste. Paste consistency is an important parameter both for application of the paste and for adhesion of the paste to the wound.

WO 2013/185776 discloses a dry paste composition suitable for wound healing and haemostatic use which reconstitutes spontaneously to form a flowable paste, i.e. without any mixing required, upon addition of an aqueous medium. The dry composition is prepared by mixing a crosslinked biocompatible polymer, one or more polyols and an aqueous medium to prepare a paste and then lyophilising the paste to obtain the dry composition.

WO 2014/202760 discloses a dry composition suitable for wound healing and haemostatic use which reconstitutes spontaneously to form a flowable paste, i.e. without any mixing needed, upon addition of an aqueous medium. The dry composition is prepared by mixing a crosslinked biocompatible polymer and an aqueous medium to prepare a paste, expanding the paste by subjecting the paste to a reduced pressure, freezing the expanded paste and then drying the expanded, frozen paste to obtain the dry composition.

As mentioned above, paste consistency can be important for the haemostatic effect and adhesion of the paste to the tissue. In addition, the consistency of the reconstituted pastes can also be an important parameter determining which types of surgeries the pastes are most suitable for. For instance, a softer paste consistency may be preferable in certain types of surgeries. Surgeon preferences also vary with regards to the consistency of the pastes, where some surgeons prefer a softer consistency than others. Thus, there is a need in the art for developing dry paste compositions, wherein the consistency of the reconstituted paste can be more easily controlled.

SUMMARY OF INVENTION

The present disclosure addresses the above problems and thus provides a dry composition, which upon addition of an aqueous medium forms a substantially homogenous paste without any mechanical mixing required. A soft and light consistency of the reconstituted paste is controlled by the presence of an alkaline and an acidic compound, which are capable of reacting to produce a gas upon wetting of the dry composition. The gas produced upon reaction of the acid and the base expands inside the composition being reconstituted and results in a paste having a desirable soft and light consistency without having to introduce air by mechanical mixing procedures.

The release of a gas upon wetting of the dry composition can be achieved in at least three alternative ways:

-   -   1. By preparing a dry composition comprising an alkaline         compound and reconstituting with a liquid comprising an acidic         compound.     -   2. By preparing a dry composition comprising an acidic compound         and reconstituting with a liquid comprising an alkaline         compound.     -   3. By preparing a dry composition comprising both an alkaline         compound and an acidic compound and reconstituting with an         aqueous medium, for instance water.

The alkaline compound and the acidic compound are capable of reacting in the presence of an aqueous medium to release a gas.

Thus, in a first embodiment, the invention relates to a method for preparing a dry composition comprising the steps of:

-   -   a) mixing a biocompatible polymer in powder form, an aqueous         medium and an alkaline compound to obtain a paste, and     -   b) drying the paste,     -   wherein the alkaline compound is capable of reacting with an         acidic compound in an aqueous medium to release a gas.

In a second embodiment, the invention relates to a method for preparing a dry composition comprising the steps of:

-   -   a) mixing a biocompatible polymer in powder form, an aqueous         medium and an acidic compound to obtain a paste, and     -   b) drying the paste,     -   wherein the acidic compound is capable of reacting with an         alkaline compound in an aqueous medium to release a gas.

In a third embodiment, a dry composition comprising either an alkaline or an acidic compound is further added:

-   -   a) an acidic compound in dry form after the paste has been dried         if the dry composition already comprises an alkaline compound,         or     -   b) an alkaline compound in dry form after the paste has been         dried if the dry composition already comprises and acidic         compound.     -   wherein the acidic compound and the alkaline compound are         capable of reacting in the presence of an aqueous medium to         release a gas.

The dry composition prepared by the above methods reconstitutes efficiently upon addition of a suitable liquid to a paste having a soft and “fluffy” consistency. The paste forms independently of external stimuli, such as mixing or stirring of any kind.

The present disclosure further relates to a dry composition obtainable by the above methods, to methods for reconstituting the dry composition and to uses thereof.

The present disclosure further relates to a paste having a desirable soft consistency and uses thereof.

DESCRIPTION OF DRAWINGS

FIG. 1. Average reconstitution time+/−standard deviation of freeze-dried gelatine pastes comprising the different polyols of example 1. The pastes have not been vacuum expanded prior to freeze-drying. Inclusion of different polyols in the freeze-dried paste composition resulted in spontaneous reconstitution of the pastes within about 30 seconds.

FIG. 2. Average reconstitution time+/−standard deviation of the lyophilised and vacuum expanded lyophilised gelatine pastes of example 3. Vacuum expansion greatly decreased the spontaneous reconstitution time of pastes comprising mannitol.

FIGS. 3 to 14 depict different embodiments of the method of the present disclosure involving vacuum expansion of the pastes prior to drying.

FIG. 3 shows two possible embodiments of a syringe for use as a container before the paste has been added. Concept 1 encompasses a standard single use syringe and concept 2 encompasses a single use syringe with a lyophilisation bypass in the syringe body. The pressure valve is closed.

FIG. 4 shows the syringes of concept 1 and 2 with an amount of paste.

FIG. 5 shows a syringe fitted with a lyophilisation plunger comprising a bypass (lyo plunger; concept 1) or a syringe comprising a bypass in the syringe body being fitted with a standard plunger (concept 2). The bypasses of both concept 1 and 2 allow for gaseous communication between the product chamber and the outside of the container. Application of low vacuum results in expansion of the paste, i.e. the volume of the paste is greater than before application of vacuum.

FIG. 6 shows the syringes of concepts 1 and 2 after the paste has been frozen. Freezing results in a locked expanded paste structure.

FIG. 7 shows the syringes of concepts 1 and 2 undergoing vacuum freeze-drying. Freeze-drying does not alter the volume of the frozen paste.

FIG. 8 shows the syringes of concepts 1 and 2, wherein the bypasses have been closed with a collapsible shelf. The syringes contain the dry paste in a product chamber with vacuum.

FIG. 9 shows the syringes of concepts 1 and 2 after the vacuum in the freeze-dryer has been released. The vacuum inside the product chamber and the atmospheric pressure outside the product chamber causes the plunger to shift until it comes into contact with the dry paste product.

FIG. 10 shows the syringes of concepts 1 and 2 after assembly of a plunger rod and flanges.

FIG. 11 shows the syringe of concept 1 being sterilised by irradiation.

FIG. 12 shows two different embodiments for reconstituting the dry paste. In a first embodiment (top), the syringe is fitted to a plastic bag holding sterile H₂O or saline. In a second embodiment (bottom), the syringe is fitted to a plastic container holding sterile H₂O or saline, wherein the plastic container is fitted with a movable plunger.

FIG. 13 shows the two embodiments from FIG. 12 after the valve has been opened. Opening of the valve results in the liquid automatically being drawn into the product chamber due to the pressure difference between the product chamber (low pressure) and the liquid container (normal pressure). The paste is spontaneously reconstituted upon contact with the liquid. Mechanical mixing is not required before use of the paste.

FIG. 14 depicts a ready to use paste within a syringe fitted with an applicator tip.

FIG. 15 shows a correlation between the pressure used for vacuum expanding a gelatine paste and the density of the final dry paste composition: The lower the pressure; the lower the density of the dry composition.

FIGS. 16a-d show perspective views of the barrel of one embodiment of the presently disclosed syringe.

FIGS. 17a-b show perspective proximal views of two different embodiments of the barrel of the presently disclosed syringe.

FIGS. 18a-b are cut-through side view illustrations of the barrel of one embodiment of the presently disclosed syringe, with the pressure valve in two different positions.

FIG. 19a shows another embodiment of a pressure valve.

FIG. 19b shows a frontal view of another embodiment of the pressure chamber of the presently disclosed syringe with the pressure valve from FIG. 19 a.

FIGS. 19c-d show cut-through frontal view of the configuration of the pressure valve from FIG. 19a inside the pressure chamber from FIG. 19 b.

FIGS. 20a-b are cut-through side view illustrations of the pressure valve from FIG. 19a inside the pressure chamber from FIG. 19.

FIGS. 20c-d are perspective view illustrations of the barrel with the pressure valve and pressure chamber from FIG. 19.

FIG. 21 shows the average reconstitution time+/−standard deviation of dried gelatine paste compositions comprising different amounts of mannitol (% w/w in wet paste) with and without vacuum expansion. Vacuum expansion greatly decreased the spontaneous reconstitution time of the dried pastes, which is even further decreased by increasing concentrations of mannitol in the dried pastes.

FIG. 22 shows the reconstitution time+/−standard deviation of vacuum expanded dried gelatine paste compositions with and without PEG (wt % in wet paste). PEG decreased the reconstitution time as compared to vacuum expanded compositions without PEG.

FIG. 23 shows the consistency of pastes reconstituted from dry compositions comprising different concentrations of NaHCO₃ (Example 7). The results show that the consistency of the pastes softens as the concentration of NaHCO₃ in the dry composition increases.

The drawings are exemplary only and should not be construed as limiting the scope of the invention.

Definitions

“Ambient pressure” is herein used interchangeably with the term “atmospheric pressure”. It is the pressure in the surrounding area, i.e. the pressure in the location in which a process takes place.

“Bar” (unit). The bar is a non-SI unit of pressure, defined as exactly equal to 100,000 Pa. It is about equal to the atmospheric pressure on Earth at sea level.

A “bioactive agent” is any agent, drug, compound, composition of matter or mixture which provides some pharmacologic, often beneficial, effect that can be demonstrated in vivo or in vitro. An agent is thus considered bioactive if it has interaction with or effect on a cell tissue in the human or animal body. As used herein, this term further includes any physiologically or pharmacologically active substance that produces a localized or systemic effect in an individual. Bioactive agents may be a protein, such as an enzyme. Further examples of bioactive agents include, but are not limited to, agents comprising or consisting of an oligosaccharide, a polysaccharide, an optionally glycosylated peptide, an optionally glycosylated polypeptide, an oligonucleotide, a polynucleotide, a lipid, a fatty acid, a fatty acid ester and secondary metabolites. It may be used either prophylactically, therapeutically, in connection with treatment of an individual, such as a human or any other animal. The term “bioactive agent” as used herein does not encompass cells, such as eukaryotic or prokaryotic cells.

“Biocompatible” refers to a material's ability to perform its intended function without eliciting any substantial undesirable local or systemic effects in the host.

“Biologically absorbable” or “resorbable” are terms which in the present context are used to describe that the materials of which the said powder are made can be degraded in the body to smaller molecules having a size which allows them to be transported into the blood stream. By said degradation and absorption the said powder materials will gradually be removed from the site of application. For example, gelatine can be degraded by proteolytic tissue enzymes to absorbable smaller molecules, whereby the gelatine, when applied in tissues, typically is absorbed within about 4-6 weeks and when applied on bleeding surfaces and mucous membranes typically within 3-5 days.

“Carbonate salt” as used herein includes carbonate (CO₃ ²⁻) and bicarbonate (HCO₃)⁻ salts.

“Expansion” is herein defined as an increase in volume and a decrease in density. Thus, if a material is said to be expanded, the total volume of the material is greater than before the expansion without affecting the total weight of the material.

A “gel” is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state. By weight, gels are mostly liquid, yet they behave like solids due to a three-dimensional cross-linked network within the liquid. It is the crosslinks within the fluid that give a gel its structure (hardness) and contribute to stickiness (tack). In this way gels are a dispersion of molecules of a liquid within a solid in which the solid is the continuous phase and the liquid is the discontinuous phase. A gel is not a paste or slurry. For example, non-crosslinked gelatin particles are soluble and may form a gel upon contact with an aqueous medium such as water. A gel does not have pores comprising expandable gas or air.

“Haemostasis” is a process which causes bleeding to diminish or stop. Haemostasis occurs when blood is present outside of the body or blood vessels and is the instinctive response for the body to stop bleeding and loss of blood. During haemostasis three steps occur in a rapid sequence. Vascular spasm is the first response as the blood vessels constrict to allow less blood to be lost. In the second step, platelet plug formation, platelets stick together to form a temporary seal to cover the break in the vessel wall. The third and last step is called coagulation or blood clotting. Coagulation reinforces the platelet plug with fibrin threads that act as a “molecular glue”. Accordingly, a haemostatic compound is capable of stimulating haemostasis.

“International Unit (IU)”. In pharmacology, the International Unit is a unit of measurement for the amount of a substance, based on biological activity or effect. It is abbreviated as IU, UI, or as IE. It is used to quantify vitamins, hormones, some medications, vaccines, blood products, and similar biologically active substances.

A “paste” according to the present disclosure has a malleable, putty-like consistency, such as toothpaste. A paste is a thick fluid mixture of pulverized solid/solid in powder form with a liquid. A paste is a substance that behaves as a solid until a sufficiently large load or stress is applied, at which point it flows like a fluid, i.e. a paste is flowable. Flowables conform efficiently to irregular surfaces upon application. Pastes typically consist of a suspension of granular material in a background fluid. The individual grains are jammed together like sand on a beach, forming a disordered, glassy or amorphous structure, and giving pastes their solid-like character. It is this “jamming together” that gives pastes some of their most unusual properties; this causes paste to demonstrate properties of fragile matter. A paste is not a gel/jelly. A “slurry” is a fluid mixture of a powdered/pulverized solid with a liquid, such as water. Slurries behave in some ways like thick fluids, flowing under gravity and being capable of being pumped if not too thick. A slurry may functionally be regarded as a thin, watery paste, but a slurry generally contains more water than a paste. A paste according to the present disclosure has pores being compartments comprising an expandable gas, such as air. Substantially water-insoluble powder particles, such as cross-linked gelatine particles, will form a paste upon mixing with an aqueous medium.

“Percentage”. If nothing else is indicated, the percentage is percentage by weight: % w/w or wt %.

Ratios are indicated as weight by weight (w/w).

A “reduced pressure” is herein considered a pressure below ambient pressure, i.e. a pressure below that of the pressure in the surrounding area in which a certain process operates.

“Spontaneous”. The term “spontaneous” is used to describe phenomena arising from internal forces or causes, which are independent of external agencies or stimuli and which happen within a short period of time, preferably within less than about 30 seconds, more preferred within less than about 20 seconds, even more preferred within less than about 10 seconds or within less than about 5 seconds, such as within less than about 3 seconds, for example less than about 2 seconds.

“Vacuum” is herein defined as a region with a gaseous pressure less than the ambient pressure, i.e. the surrounding atmospheric pressure. At sea level on Earth the atmospheric pressure is approximately 1 bar, i.e. 1000 mbar at 25° C. The below table shows the approximate pressures in “low”, “medium” and “high” vacuum at sea level on earth in millibar (mbar).

pressure (mbar) Atmospheric pressure 1000 Low vacuum 1000 to 100 Medium vacuum   100 to 0.001 High vacuum <0.001

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure provides a dry composition, which upon addition of an adequate amount of an aqueous medium forms a substantially homogenous paste, which is soft and light (“fluffy” or airy”). The dry composition is capable of reconstituting without any mechanical mixing required.

Reconstitution without mechanical mixing and a soft consistency of the reconstituted paste can be achieved by contacting an acid and a base which are capable of reacting with each other to produce a gas in the presence of an aqueous medium. The acid and the base are capable of reacting with each other when the dry composition is wetted, i.e. upon reconstitution of the dry composition.

In a preferred embodiment, the dry composition is prepared with a carbonate salt as the base. Upon addition of an aqueous medium comprising an acid, the acid reacts with the carbonate ion to create carbonic acid, which readily decomposes to CO₂. The CO₂ gas expands inside the paste, thereby allowing for efficient distribution of liquid inside the dry composition. The resulting paste has a soft desirable consistency.

The advantages of the dry composition and the reconstituted paste obtained by the methods of the present disclosure are numerous and include:

-   -   Less time is spent preparing the paste which means that bleeding         can be stopped faster.     -   Decreased risk of compromising the sterility of the paste during         preparation due to less handling steps.     -   Decreased risk of making mistakes during preparation of the         paste.     -   Optimal consistency of paste obtained every time.     -   Reliable and consistent reconstitution within a short time         period.     -   Bioactive agents, which are unstable in solution may be added to         the paste prior to drying and will thus be present in the dry         composition of the invention. For example, thrombin may be added         to the paste prior to drying, thereby avoiding the         time-consuming and error-prone thrombin dilution steps.     -   Minimises Operation Room costs since preparation of the         currently described product is so simple and fast that there is         no reason to pre-prepare haemostatic flowables before surgery         which may not be used.     -   Reconstituted paste has a soft consistency, which may be         desirable in certain types of surgeries.

All of the above factors lead to increased patient safety.

Biocompatible Polymer

A paste can be formed from a biocompatible polymer when the biocompatible polymer is in powder form and the powder particles are substantially insoluble in the aqueous medium they are mixed with. Thus, the biocompatible polymer in powder form consists of substantially water-insoluble powder particles. Preferably, the agent is a cross-linked biocompatible polymer suitable for use in haemostasis and/or wound healing, such as a cross-linked haemostatic agent in powder form, for example a cross-linked gelatine powder. Cross-linking renders the biocompatible polymer substantially insoluble in an aqueous medium.

The biocompatible polymer in powder form consists of solid, porous or non-porous particles of a biocompatible polymer suitable for use in haemostasis and wound healing procedures.

In one embodiment, the composition of the present disclosure comprises one or more biocompatible polymers in powder form, such as a single biocompatible polymer or a combination of two or more biocompatible polymers.

The biocompatible polymer of the present disclosure may be a biologic or a non-biologic polymer. Suitable biologic polymers include proteins, such as gelatin, collagen, albumin, hemoglobin, casein, fibrinogen, fibrin, fibronectin, elastin, keratin, and laminin; or derivatives or combinations thereof. Particularly preferred is the use of gelatin or collagen, more preferably gelatin. Other suitable biologic polymers include polysaccharides, such as glycosaminoglycans, starch derivatives, xylan, cellulose derivatives, hemicellulose derivatives, agarose, alginate, and chitosan; or derivatives or combinations thereof. Suitable non-biologic polymers will be selected to be degradable by either of two mechanisms, i.e. (1) break down of the polymeric backbone or (2) degradation of side chains which result in aqueous solubility. Exemplary nonbiologic polymers include synthetics, such as polyacrylates, polymethacrylates, polyacrylamides, polyvinyl resins, polylactide-glycolides, polycaprolactones, and polyoxyethylenes; or derivatives or combinations thereof. Also combinations of different kinds of polymers are possible.

In a preferred embodiment the biocompatible polymer is biologically absorbable. Examples of suitable biologically absorbable materials include gelatine, collagen, chitin, chitosan, alginate, cellulose, oxidised cellulose, polyglycolic acid, polyacetic acid and combinations thereof. It will be understood that various forms thereof, such as linear or cross-linked forms, salts, esters and the like are also contemplated for the present disclosure. In a preferred embodiment, the biologically absorbable material is gelatine. Gelatine is highly biologically absorbable. Furthermore, gelatine is highly biocompatible, meaning that it is non-toxic to an animal, such as a human being, when/if entering the blood stream or being in long-term contact with human tissues.

The gelatine typically originates from a porcine source, but may originate from other animal sources, such as from bovine or fish sources. The gelatine may also be synthetically made, i.e. made by recombinant means.

In a preferred embodiment the biocompatible polymer is cross-linked. Cross-linking usually renders the polymer substantially insoluble in an aqueous medium. Any suitable cross-linking methods known to a person of skill may be used including both chemical and physical cross-linking methods.

In one embodiment of the present disclosure the polymer has been cross-linked by physical means, such as by dry heat. The dry heat treatment is usually performed at temperatures between 100° C. and 250° C., such as about 110° C. to about 200° C. In particular the temperature may be in the range of 110-160° C., e.g. in the range of 110-140° C., or in the range of 120-180° C., or in the range of 130-170° C., or in the range of 130-160° C., or in the range of 120-150° C. The period of time for cross-linking may be optimised by a skilled person and is normally a period between about 10 minutes to about 12 hours, such as about 1 hour to about 10 hours, for example between about 2 hours to about 10 hours, such as between about 4 hours to about 8 hours, for example between about 5 hours to about 7 hours, such as about 6 hours.

In another embodiment, the polymer has been cross-linked by chemical means, i.e. by exposure to a chemical cross-linking agent. Examples of suitable chemical cross-linking agents include but are not limited to aldehydes, in particular glutaraldehyde and formaldehyde, acyl azide, caboiimides, hexamethylene diisocyanate, polyether oxide, 1,4-butanedioldiglycidyl ether, tannic acid, aldose sugars, e.g. D-fructose, genipin and dye-mediated photo-oxidation. Specific compounds include but are not limited to I-(3-dimethylaminopropyl)-3-ethylcarboiimide hydrochloride (EDC), dithiobis(propanoic dihydrazide) (DTP), I-ethyl-3-(3-dimethylamino-propyl)-carbodiimide (EDAC).

In a preferred embodiment, the biocompatible polymer is obtained from cross-linked sponges of gelatine or collagen, in particular cross-linked sponges of gelatine (such as the commercially available Spongostan® sponges and Surgifoam® sponges). The cross-linked sponges are micronized by methods known in the art to obtain a cross-linked biocompatible polymer in powder form, such as by rotary bed, extrusion, granulation and treatment in an intensive mixer, or milling (e.g. by using a hammer mill or a centrifugal mill).

Spongostan®/Surgifoam® available from Ethicon is a gelatine based cross-linked absorbable haemostatic sponge. It absorbs >35 g of blood/g and within 4-6 weeks it is completely absorbed in the human body.

In one embodiment, the biocompatible polymer in powder form comprises or consists of gelatine particles obtained from a micronized porous gelatine sponge, which has been cross-linked by dry heat treatment. Such gelatine particles will be porous.

Micronized porous gelatine sponges may be prepared by mixing an amount of soluble gelatine with an aqueous medium in order to create a foam comprising a discontinuous gas phase, drying said foam and crosslinking the dried foam by exposure to dry heat, thereby obtaining a dry crosslinked sponge. The obtained crosslinked sponge can be micronized by methods known in the art. The gelatine foam usually has a gelatine concentration from about 1% to 70% by weight, usually from 3% to 20% by weight. Drying is usually performed at about 20° C. to about 40° C. for about 5 to 20 hours. The dried foam is usually crosslinked by exposure to a temperature of about 110° C. to about 200° C. for about 15 minutes to about 8 hours, such as at about 150° C. to about 170° C. for about 5 to 7 hours.

In another embodiment, the biocompatible polymer comprises or consists of cross-linked gelatine particles obtained from a gelatine hydrogel. A gelatine hydrogel may be prepared by dissolving an amount of gelatine in an aqueous buffer to form a non-cross-linked hydrogel, typically having a solids content from 1% to 70% by weight, usually from 3% to 10% by weight. The gelatin is cross-linked, for example by exposure to either glutaraldehyde (e.g. 0.01% to 0.05% w/w, overnight at 0 DEG to 15 DEG C. in aqueous buffer), sodium periodate (e.g. 0.05 M, held at 0 DEG C. to 15 DEG C. for 48 hours) or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (“EDC”) (e.g., 0.5% to 1.5% w/w, overnight at room temperature), or by exposure to about 0.3 to 3 megarads of gamma or electron beam radiation. The resulting crosslinked hydrogels may be fragmented and dried to obtain a gelatine powder. Alternatively, gelatin particles can be suspended in an alcohol, preferably methyl alcohol or ethyl alcohol, at a solids content of 1% to 70% by weight, usually 3% to 10% by weight, and cross-linked by exposure to a cross-linking agent, typically glutaraldehyde (e.g., 0.01% to 0.1% w/w, overnight at room temperature). When cross-linking with glutaraldehyde, the cross-links are formed via Schiff bases which may be stabilized by subsequent reduction, e.g. by treatment with sodium borohydride. After cross-linking, the resulting granules may be washed in water and optionally rinsed in an alcohol and dried to obtain a gelatine powder. In one embodiment, crosslinked gelatine particles are prepared essentially as described in U.S. Pat. No. 6,066,325. Such gelatine particles will be non-porous.

The cross-linked powder particles are in one embodiment less than approximately 1000 microns in size, i.e. so that they are able to pass through a 1×1 mm sieve.

In one embodiment at least 90% of the powder particles have a diameter of between 1 μm and 1200 μm.

In one embodiment, the average particle diameter is between 1 μm and 1000 μm, such as between 10 μm and 800 μm, for example between 50 μm and 600 μm, such as between 100 μm and 500 μm, for example between 200 μm and 400 μm, such as about 300 μm.

In some applications it is desirable to have a smaller particle size, whereby a smoother paste can be obtained. Thus in one embodiment, the average particle diameter is less than 100 μm, such as less than 50 μm, for example less than 30 μm, such as less than 20 μm, for example less than 10 μm. One example of an application where a smoother paste is desirable is in the control of bone bleeding.

Particles of a certain size distribution can be achieved by passing a powdered composition through one or more sieves having a certain mesh size and collecting the powder which passes through and/or is retained by a certain mesh size. For example, powder particles having a size distribution between approximately 200 μm and 1000 μm can be obtained by collecting the powder which is able to pass through a 1×1 mm sieve but is retained by a 0.2×0.2 mm sieve.

In one embodiment, the paste obtained by mixing the biocompatible polymer in powder form and the aqueous medium comprises between about 10% to about 60% of the biocompatible polymer, for example about 10% to about 50% of the biocompatible polymer, such as about 10% to about 40% of the biocompatible polymer, for example about 10% to about 30% of the biocompatible polymer, such as about 12% to about 25% of the biocompatible polymer, for example about 14% to about 25% of the biocompatible polymer, such as about 15% to about 25% of the biocompatible polymer, for example about 16% to about 20% of the biocompatible polymer, such as about 17% to about 20% of the biocompatible polymer, for example about 18% to about 20% of the biocompatible polymer.

In one embodiment, the paste obtained by mixing the biocompatible polymer in powder form and the aqueous medium comprises more than 10% of the biocompatible polymer, such as more than 15% of the biocompatible polymer, for example more than 16% of the biocompatible polymer, such as more than 17% of the biocompatible polymer, for example more than 18% of the biocompatible polymer, such as more than 19% of the biocompatible polymer, for example more than 20% of the biocompatible polymer.

In one embodiment, the paste obtained by mixing the biocompatible polymer in powder form and the aqueous medium comprises less than 40% of the biocompatible polymer, such as less than 30% of the biocompatible polymer, for example less than 25% of the biocompatible polymer, such as less than 20% of the biocompatible polymer.

In a preferred embodiment, the paste obtained by mixing the biocompatible polymer in powder form and the aqueous medium comprises between about 10% to about 30% of the biocompatible polymer, more preferred between about 15% to about 25% of the biocompatible polymer, such as about 20% of the biocompatible polymer.

After drying, the composition comprises between about 40% and 80% of the biocompatible polymer, such as between about 45% and 80% of the biocompatible polymer, for example between about 50% and 80% of the biocompatible polymer, such as between about 55% and 80% of the biocompatible polymer.

In one embodiment, the dry composition comprises between about 40% and 80% of the biocompatible polymer, such as between about 45% and 75% of the biocompatible polymer, for example between about 50% and 70% of the biocompatible polymer.

In one embodiment, the dry composition of the present disclosure comprises more than about 30% of the biocompatible polymer, such as more than about 40% of the biocompatible polymer, for example more than about 45% of the biocompatible polymer, such as more than about 50% of the biocompatible polymer, for example more than about 55% of the biocompatible polymer, such as more than about 60% of the biocompatible polymer, for example more than about 65% of the biocompatible polymer, such as more than about 70% of the biocompatible polymer, for example more than about 75% of the biocompatible polymer, such as more than about 80% of the biocompatible polymer.

In one embodiment, the dry composition of the present disclosure comprises less than about 80% of the biocompatible polymer, such as less than about 70% of the biocompatible polymer, for example less than about 65% of the biocompatible polymer, such as less than about 60% of the biocompatible polymer, for example less than about 55% of the biocompatible polymer, such as less than about 50% of the biocompatible polymer.

Acid-Base Reactions Capable of Forming a Gas

Introduction of a gas into the reconstituted paste without mechanical mixing is achieved by the presence of an alkaline compound and an acidic compound, wherein said alkaline compound and said acidic compound are capable of producing a gas in the presence of an aqueous medium.

When the dry composition of the present disclosure is reconstituted by adding an aqueous medium, a gas is produced as a result of the reaction of the acidic compound and the alkaline compound. The gas expands inside the composition being reconstituted resulting in a paste having a soft and light consistency without the need for mechanically introducing air into the composition, e.g. by transfer of the composition between two connected syringes.

The release of a gas upon wetting of the dry composition can be achieved in at least three alternative ways:

-   -   1. By preparing a dry composition comprising an alkaline         compound and reconstituting with an aqueous medium comprising an         acidic compound.     -   2. By preparing a dry composition comprising an acidic compound         and reconstituting with an aqueous medium comprising an alkaline         compound.     -   3. By preparing a dry composition comprising both an alkaline         compound and an acidic compound and reconstituting with an         aqueous medium.

For all three options, the alkaline compound and the acidic compound must be capable of reacting with each other to produce a gas in the presence of an aqueous medium.

For the third alternative it is important that the alkaline compound and the acidic compound are not contacted with an aqueous medium before gas release is desired, i.e. before reconstitution. The third alternative can e.g. be achieved by mixing an alkaline compound into the wet paste, drying the paste and adding an acidic compound in dry form to the dried paste or the reverse, by mixing an acidic compound into the wet paste, drying the paste and adding an alkaline compound in dry form to the dried paste. The alkaline compound and the acidic compound will not react in dry conditions and will only react upon wetting of the composition. The acidic or alkaline compound added in dry form should be at least partially soluble in water.

In one embodiment, the dry composition comprises from about 0.1% to about 10% of an alkaline compound, for example from about 0.5% to about 8% of an alkaline compound, such as from about 1% to about 6% of an alkaline compound or from about 1% to about 5% of an alkaline compound. Optionally the dry composition further comprises from about 0.1% to about 10% of an acidic compound, for example from about 0.5% to about 8% of an acidic compound, such as from about 1% to about 5% of an acidic compound, wherein the acidic compound is added in dry form after the paste has been dried.

In one embodiment, the dry composition comprises at least 1% of an alkaline compound, for example at least 1.5% of an alkaline compound, such as at least 2% of an alkaline compound, for example at least 2.5% of an alkaline compound, such as at least 3% of an alkaline compound, for example at least 3.5% of an alkaline compound, such as at least 4% of an alkaline compound, for example at least 4.5% of an alkaline compound, such as at least 5% of an alkaline compound. Optionally the dry composition further comprises an acidic compound as described above.

In one embodiment, the dry composition comprises less than 10% of an alkaline compound, for example less than 8% of an alkaline compound, such as less than 7% of an alkaline compound, for example less than 6% of an alkaline compound, such as less than 5% of an alkaline compound, for example less than 4% of an alkaline compound, such as less than 3% of an alkaline compound. Optionally the dry composition further comprises an acidic compound as described above.

In one embodiment, the dry composition comprises from about 0.1% to about 10% of an acidic compound, for example from about 0.5% to about 8% of an acidic compound, such as from about 0.5% to about 5% of an acidic compound or from about 1% to about 5% of an acidic compound. Optionally, the dry composition further comprises from about 0.1% to about 10% of an alkaline compound, for example from about 0.5% to about 8% of an alkaline compound, such as from about 1% to about 5% of an alkaline compound, wherein the alkaline compound is added in dry form after the paste has been dried.

In one embodiment, the dry composition comprises at least 0.1% of an acidic compound, for example at least 0.2% of an acidic compound, such as at least 0.3% of an acidic compound, for example at least 0.4% of an acidic compound, for example at least 0.5% of an acidic compound, such as at least 0.6% of an acidic compound, for example at least 0.7% of an acidic compound, such as at least 0.8% of an acidic compound, for example at least 0.9% of an acidic compound, such as at least 1.0% of an acidic compound, for example at least 1.5% of an acidic compound. Optionally the dry composition further comprises an alkaline compound as described above.

In one embodiment, the dry composition comprises less than 10% of an acidic compound, for example less than 8% of an acidic compound, such as less than 7% of an acidic compound, for example less than 6% of an acidic compound, such as less than 5% of an acidic compound, for example less than 4% of an acidic compound, such as less than 3% of an acidic compound. Optionally the dry composition further comprises an acidic compound as described above.

In a preferred embodiment, the gas produced is carbon dioxide (CO₂). One way of producing CO₂ is by contacting a carbonate salt with an acidic compound in the presence of an aqueous medium. Thus, in a preferred embodiment, the alkaline compound is a carbonate salt, even more preferred a pharmaceutically acceptable carbonate salt.

Upon contact of a carbonate salt with an aqueous medium comprising an acidic compound, i.e. an acidic solution, the carbonate in the dry composition will react with the acid to create carbonic acid, which readily decomposes to CO₂. The CO₂ gas expands inside the composition being reconstituted, thereby ensuring a soft and light consistency of the reconstituted paste. For example, reaction of sodium bicarbonate (also known as sodium hydrogen carbonate or common baking soda) and an acid produces sodium chloride and carbonic acid, which readily decomposes to carbon dioxide and water: NaHCO₃+HCl→NaCl+H₂CO₃ H₂CO₃→H₂O+CO₂(g)

For example, if sodium bicarbonate is contacted with acetic acid in an aqueous medium, the result will be sodium acetate, water, and carbon dioxide: NaHCO₃+CH₃COOH→CH₃COONa+H₂O+CO₂(g)

In one embodiment, the carbonate salt is selected from the group consisting of sodium bicarbonate (NaHCO₃), sodium carbonate (Na₂CO₃), potassium bicarbonate (KHCO₃), potassium carbonate (K₂CO₃), calcium bicarbonate (Ca(HCO₃)₂), calcium carbonate (CaCO₃), magnesium carbonate (MgCO₃), magnesium bicarbonate (Mg(HCO₃)₂), ammonium bicarbonate (NH₄HCO₃), ammonium carbonate ((NH₄)₂CO₃), gadolinium bicarbonate (Gd(HCO₃)₃, gadolinium carbonate (Gd₂(CO₃)₃), lithium bicarbonate (LiHCO₃), lithium carbonate (LiCO₃), rubidium bicarbonate (RbHCO₃), rubidium carbonate (Rb₂CO₃), zinc carbonate (ZnCO₃), zinc bicarbonate (Zn(HCO₃)₂, iron (II) carbonate (FeCO₃), iron (II) bicarbonate (Fe(HCO₃)₂), silver carbonate (Ag₂CO₃), silver bicarbonate (AgHCO₃), gold (III) carbonate Au₂(CO₃)₃, gold (I) carbonate (Au₂CO₃) and mixtures thereof.

In one embodiment, the cation of the carbonate salt is a metal.

In one embodiment, the cation of the carbonate salt is sodium, i.e. the carbonate salt is sodium bicarbonate or sodium carbonate, preferably sodium bicarbonate.

In one embodiment, the cation of the carbonate salt is calcium, i.e. the carbonate salt is calcium bicarbonate or calcium carbonate. Since calcium is an activator of thrombin, the presence of calcium in the reconstituted paste may be beneficial in embodiments comprising thrombin as it may lead to enhanced thrombin activity.

In one embodiment, the cation of the carbonate salt is potassium, i.e. the carbonate salt is potassium bicarbonate (KHCO₃) or potassium carbonate (K₂CO₃).

In one embodiment, the carbonate salt is at least partially soluble in water. For instance, the carbonate salt has a solubility in water at 20° C. and at 1 atmosphere pressure above about 1 g/100 g water, for example at least about 5 g/100 g water. For instance, sodium bicarbonate has a solubility of about 9.6 g/100 g water at 20° C. and at 1 atmosphere pressure. When a carbonate salt is added in dry form to a dry composition comprising an acidic compound it is important that the carbonate salt is at least partially soluble in water for it to effectively come into contact with the acidic compound distributed within the dry composition when the composition is wetted, i.e. reconstituted.

In other embodiments, the carbonate salt is essentially not soluble in water. For instance, calcium carbonate has a solubility of less than 0.001 g/100 g water at 20° C. and at 1 atmosphere pressure and silver carbonate has a solubility of less than 0.01 g/100 g water at 20° C. and at 1 atmosphere pressure. When a dry composition is prepared with a carbonate salt essentially homogenously distributed therein, i.e. by adding the carbonate salt to the paste before drying, the carbonate salt does not have to be soluble in water.

In one embodiment, the dry composition comprises from about 0.1% to about 10% of a carbonate salt, for example from about 0.5% to about 8% of a carbonate salt, such as from about 1% to about 6% or 1% to about 5% of a carbonate salt. Optionally, the dry composition further comprises an acidic compound in dry form.

When a dry composition comprising a carbonate salt is contacted with an acidic compound in the presence of an aqueous medium, CO₂ will be produced as explained above. The dry composition comprising a carbonate salt may either be reconstituted with an aqueous medium comprising an acidic compound, i.e. an acidic solution (1^(st) alternative) or if the dry composition comprising a carbonate salt is further added an acidic compound in dry form after drying, the dry composition may be reconstituted with an aqueous medium which neither comprises an acidic nor an alkaline compound (3^(rd) alternative). In the latter case, an acidic solution will form upon addition of the aqueous medium as the acid will dissolve in the aqueous medium.

In one embodiment, the dry composition comprising a carbonate salt is reconstituted by addition of an acidic solution having a pH in the range of from about 1 to about 6, such as a pH from about 1.5 to about 5, for example a pH from about 2 to about 4. The optimal pH of the reconstitution liquid can be determined by the skilled person by balancing the need for efficient gas development during reconstitution and the desire to have a reconstituted paste with a pH as close to 7 as possible.

In one embodiment, the dry composition comprising an alkaline compound, such as a carbonate salt is reconstituted by addition of an acidic solution comprising between about 1% to about 10% of an acidic compound, such as from about 1% to about 8% of an acidic compound, for example from about 1.5% to about 6% of an acidic compound, such as from about 2% to about 5% of an acidic compound, for example from about 2% to about 4% of an acidic compound.

In one embodiment the acidic solution has a pH of from about 1 to about 4, such as from about 1 to about 3, for example from about 1.5 to about 2.5, such as about 2.

In one embodiment the acidic solution has a pH lower than about 4, such as lower than about 3, for example lower than about 2.5.

Preferably, the alkaline and acidic compounds used in the present invention are physiologically acceptable compounds. The term physiologically acceptable is used interchangeably herein with the term pharmaceutically acceptable.

In one embodiment, the acidic compound in the reconstitution liquid is selected from the group consisting of acetic acid, citric acid, tartaric acid and oxalic acid.

In one embodiment, the acidic compound is acetic acid.

In one embodiment, the acidic compound is citric acid.

In one embodiment, the acidic compound is tartaric acid.

In one embodiment, the acidic compound is oxalic acid.

According to the second alternative above, a dry composition comprising an acidic compound is prepared and said dry composition is contacted with alkaline compound upon reconstitution of the dry composition. For instance, the dry composition comprising an acidic compound can be reconstituted with an aqueous medium comprising an alkaline compound, for instance an aqueous medium comprising a carbonate salt. If the dry composition comprising an acidic compound is further added an alkaline compound in dry form after drying of the composition, the dry composition may be reconstituted with an aqueous medium which neither comprises an acidic nor an alkaline compound (3^(rd) alternative). It is important, however, that the alkaline compound is at least partially soluble in water to allow for the alkaline compound to effectively come into contact with the acidic compound distributed within the dry composition upon wetting of the composition.

In one embodiment, the dry composition comprises an acidic compound selected from the group consisting of acetic acid, citric acid, oxalic acid and tartaric acid. This composition may suitably be reconstituted by addition of a solution comprising an alkaline compound such as a carbonate salt.

In one embodiment the dry composition comprises acetic acid.

In one embodiment the dry composition comprises citric acid.

In one embodiment the dry composition comprises oxalic acid.

In one embodiment the dry composition comprises tartaric acid.

The dry composition comprising an acidic compound may be reconstituted by addition of an alkaline solution comprising between about 1% to about 10% of an alkaline compound, such as from about 1% to about 8% of an alkaline compound, for example from about 1.5% to about 6% of an alkaline compound, such as from about 2% to about 5% of an alkaline compound, for example from about 2% to about 4% of an alkaline compound.

In one embodiment the alkaline solution has a pH of from about 7.5 to about 9, such as from about 8 to about 9, for example from about 8 to about 9.5.

In one embodiment the alkaline solution has a pH higher than about 7.5, such as higher than about 7.8, for example higher than about 8.0, such as higher than about 8.5.

In an alternative embodiment, the reaction of an alkaline compound and an acidic compound causes the production of a noble gas, such as helium (He), neon (Ne) or argon (Ar).

In yet another embodiment, the reaction of an alkaline compound and an acidic compound causes the production of hydrogen (H₂), nitrogen (N₂) or oxygen (O₂).

Aqueous Medium

An aqueous medium is used in the method of the present disclosure for initially preparing the paste, which is subsequently dried to obtain a dry composition. An aqueous medium is also used for reconstituting the dry composition.

The aqueous medium of the present disclosure may be any aqueous medium suitable for preparing a paste known to a person of skill, e.g. water or saline. The water may for example be WFI (Water For Injection). The aqueous medium is preferably sterile and compatible with surgical use.

The aqueous medium of the present disclosure is in one embodiment a saline solution.

In one embodiment, the aqueous medium is a calcium chloride solution.

In one embodiment, the aqueous medium is water.

The aqueous medium is initially mixed with the agent in powder form in sufficient amounts to obtain a wet paste. For procedural efficiency, it is sometimes desirable that the paste prior to drying contains less water, i.e. is thicker, than a paste intended for e.g. surgical use would be so that less water has to be removed in the drying process.

In one embodiment, the paste of the present disclosure prior to drying comprises less than 99% of water, preferably less than 95% of water.

In one embodiment, the paste of the present disclosure prior to drying comprises between about 50% to about 90% of water, such as between about 55% to about 85% of water, for example between about 60% to about 80% of water, such as about 70% of water.

After drying, the dry composition comprises less than about 5% of water, such as less than about 3% of water, preferably less than about 2% of water, more preferred less than about 1.5% of water, even more preferred less than about 1% of water or even less. Hence, in one embodiment, the dry composition comprises from about 0.1 to about 5% water, such as from about 0.1% to about 2% water.

A low residual water content in the haemostatic composition after drying is desirable as it decreases the risk of microbial growth in the dry composition. Furthermore, a low residual water content is essential if the composition comprises bioactive agents that are unstable in aqueous conditions, such as e.g. thrombin. If thrombin is present in the composition of the present disclosure, the residual water content in the dried composition is preferably less than about 3% water, more preferred less than 2% water, such as less than 1% water.

In one embodiment, the residual water content in the dry composition is about 0.5% or less. Such low residual water content is possible with e.g. industrial freeze-drying apparatuses.

Hydrophilic Compounds

In one embodiment, the dry composition of the present disclosure comprises one or more hydrophilic compounds. Hydrophilic compounds usually contain polar or charged functional groups, rendering them soluble in water. Inclusion of one or more hydrophilic compounds in the paste prior to drying of said paste has a beneficial effect on the wettability of the paste, thus enhancing reconstitution efficiency and reconstitution rate of the dry composition.

In one embodiment, the hydrophilic compound is a hydrophilic polymer. The hydrophilic polymer may be natural or synthetic, linear or branched, and have any suitable length.

In one embodiment, the hydrophilic polymer is selected from the group consisting of Polyethylenimine (PEI), Poly(ethylene glycol) (PEG), Poly(ethylene oxide), Poly(vinyl alcohol) (PVA), Poly(styrenesulfonate) (PSS), Poly(acrylic acid) (PAA), Poly(allylamine hydrochloride) and Poly(vinyl acid). In one embodiment, the hydrophilic compound is polyethylene glycol (PEG).

In one embodiment, the hydrophilic compound is selected from the group consisting of Cetylpyridinium Chloride, Docusate Sodium, Glycine, Hypromellose, Hypromellose, Phthalate, Lechitin, Phospholipids, Poloxamer, Polyoxyethylene Alkyl Ethers, Polyoxyethylene Castor Oil Derivatives, Polyoxyethylene Sorbitan Fatty Acid Esters, Polyoxyethylene Stearates, Polyvinyl Alcohol, Sodium Lauryl Sulfate, Sorbitan Esters (Sorbitan Fatty Acid Esters) and Tricaprylin.

In one embodiment, the hydrophilic compound is not a polymer.

In one embodiment, the hydrophilic compound is not a macromolecule.

In one embodiment, the hydrophilic compound has a molecular weight of less than 1000 Da, such as less than 500 Da.

In one embodiment, the hydrophilic compound is an oligomer, such as an oligomer consisting of less than 10 monomeric subunits, for example less than 5 monomeric subunits.

In one embodiment, the hydrophilic compound is a dimer, a trimer or a tetramer.

In one embodiment, the hydrophilic compound is a monomer.

In one embodiment, the hydrophilic compound comprises less than 20 C atoms, such as 18 C atoms or less or 12 C atoms or even less, such as 6 C atoms.

In a preferred embodiment, the hydrophilic compound is a polyol. Thus, according to one embodiment, one or more polyols may be included in the paste prior drying of the paste. Polyols greatly enhance the reconstitution rate of the dry paste composition and also play a role in ensuring an optimal consistency of the reconstituted paste.

A polyol as defined herein is a compound with multiple hydroxyl functional groups.

Polyols include sugars (mono-, di- and polysaccharides) and sugar alcohols and derivatives thereof. Preferably, the polyol is not a polysaccharide.

Monosaccharides include but are not limited to glucose, fructose, galactose, xylose and ribose.

Disaccharides include but are not limited to sucrose (saccharose), lactulose, lactose, maltose, trehalose and cellobiose.

Polysaccharides include but are not limited to starch, glycogen, cellulose and chitin.

A sugar alcohol, also known as a polyalcohol is a hydrogenated form of carbohydrate, whose carbonyl group (aldehyde or ketone, reducing sugar) has been reduced to a primary or secondary hydroxyl group (hence the alcohol). Sugar alcohols have the general formula H(HCHO)_(n+1)H, whereas sugars have H(HCHO)_(n)HCO. Some common sugar alcohols which may be used in the method of the present disclosure include but are not limited to: Glycol (2-carbon), Glycerol (3-carbon), Erythritol (4-carbon), Threitol (4-carbon), Arabitol (5-carbon), Xylitol (5-carbon), Ribitol (5-carbon), Mannitol (6-carbon), Sorbitol (6-carbon), Dulcitol (6-carbon), Fucitol (6-carbon), Iditol (6-carbon), Inositol (6-carbon; a cyclic sugar alcohol), volemitol (7-carbon), Isomalt (12-carbon), Maltitol (12-carbon), Lactitol (12-carbon), Polyglycitol.

In one embodiment, the dry composition comprises a single hydrophilic compound, such as a single polyol.

In one embodiment, the dry composition comprises more than one hydrophilic compound, such as two, three, four, five, six or even more different hydrophilic compounds.

In a preferred embodiment, the hydrophilic compound is a polyol.

In one embodiment, the dry composition comprises two polyols, for example mannitol and glycerol or trehalose and a glycol.

In one embodiment, the dry composition comprises one or more sugar alcohols, such as one or more sugar alcohols selected from the group consisting of Glycol, Glycerol, Erythritol, Threitol, Arabitol, Xylitol, Ribitol, Mannitol, Sorbitol, Dulcitol, Fucitol, Iditol, Inositol, volemitol, Isomalt, Maltitol, Lactitol, Polyglycitol.

In one embodiment, the dry composition comprises one or more sugar alcohols and one or more sugars, such as one sugar alcohol and one sugar.

In one embodiment, the dry composition comprises one sugar alcohol and optionally one or more additional hydrophilic compounds, such as one or more polyols, which may be either sugar alcohols or sugars.

In one embodiment, the dry composition does not comprise a sugar as the only polyol.

In one embodiment of the invention, the dry composition comprises mannitol.

In one embodiment of the invention, the dry composition comprises sorbitol.

In one embodiment of the invention, the dry composition comprises glycerol.

In one embodiment of the invention, the dry composition comprises trehalose.

In one embodiment of the invention, the dry composition comprises glycol, such as propylene glycol.

In one embodiment of the invention, the dry composition comprises xylitol.

In one embodiment of the invention, the dry composition comprises maltitol.

In one embodiment of the invention, the dry composition comprises sorbitol.

In one embodiment the paste according to the invention prior to drying comprises from about 1% to about 40% of one or more hydrophilic compounds, for example from about 1% to about 30% of one or more hydrophilic compounds, such as from about 1% to about 25% of one or more hydrophilic compounds, for example from about 1% to about 20% of one or more hydrophilic compounds, such as from about 1% to about 15% of one or more hydrophilic compounds, such as from about 1% to about 14% of one or more hydrophilic compounds, for example from about 1% to about 13% of one or more hydrophilic compounds, such as from about 1% to about 12% of one or more hydrophilic compounds, for example from about 1% to about 11% of one or more hydrophilic compounds, such as about 1% to about 10% of one or more hydrophilic compounds.

In one embodiment the paste according to the invention prior to drying comprises from about 2% to about 40% of one or more hydrophilic compounds, for example from about 2% to about 30% of one or more hydrophilic compounds, such as from about 2% to about 25% of one or more hydrophilic compounds, for example from about 2% to about 20% of one or more hydrophilic compounds, such as from about 2% to about 18% of one or more hydrophilic compounds, for example from about 2% to about 17% of one or more hydrophilic compounds, such as from about 2% to about 16% of one or more hydrophilic compounds, for example from about 2% to about 15% of one or more hydrophilic compounds, such as from about 2% to about 14% of one or more hydrophilic compounds, for example from about 2% to about 13% of one or more hydrophilic compounds, such as from about 2% to about 12% of one or more hydrophilic compounds, for example from about 2% to about 11% of one or more hydrophilic compounds, such as about 2% to about 10% of one or more hydrophilic compounds.

In one embodiment the paste according to the invention prior to drying comprises from about 3% to about 40% of one or more hydrophilic compounds, for example from about 3% to about 30% of one or more hydrophilic compounds, such as from about 3% to about 25% of one or more hydrophilic compounds, for example from about 3% to about 20% of one or more hydrophilic compounds, such as from about 3% to about 18% of one or more hydrophilic compounds, for example from about 3% to about 17% of one or more hydrophilic compounds, such as from about 3% to about 16% of one or more hydrophilic compounds, for example from about 3% to about 15% of one or more hydrophilic compounds, such as from about 3% to about 14% of one or more hydrophilic compounds, for example from about 3% to about 13% of one or more hydrophilic compounds, such as from about 3% to about 12% of one or more hydrophilic compounds, for example from about 3% to about 11% of one or more hydrophilic compounds, such as about 3% to about 10% of one or more hydrophilic compounds.

In one embodiment the paste according to the invention prior to drying comprises from about 4% to about 40% of one or more hydrophilic compounds, for example from about 4% to about 30% of one or more hydrophilic compounds, such as from about 4% to about 25% of one or more hydrophilic compounds, for example from about 4% to about 20% of one or more hydrophilic compounds, such as from about 4% to about 18% of one or more hydrophilic compounds, for example from about 4% to about 17% of one or more hydrophilic compounds, such as from about 4% to about 16% of one or more hydrophilic compounds, for example from about 4% to about 15% of one or more hydrophilic compounds, such as from about 4% to about 14% of one or more hydrophilic compounds, for example from about 4% to about 13% of one or more hydrophilic compounds, such as from about 4% to about 12% of one or more hydrophilic compounds, for example from about 4% to about 11% of one or more hydrophilic compounds, such as about 4% to about 10% of one or more hydrophilic compounds.

In one embodiment, the paste according to the invention prior to drying comprises more than about 5% of one or more hydrophilic compounds, hence in one embodiment the paste according to the invention prior to drying comprises from about 5% to about 40% of one or more hydrophilic compounds, for example from about 5% to about 30% of one or more hydrophilic compounds, such as from about 5% to about 25% of one or more hydrophilic compounds, for example from about 5% to about 20% of one or more hydrophilic compounds, such as from about 5% to about 18% of one or more hydrophilic compounds, for example from about 5% to about 17% of one or more hydrophilic compounds, such as from about 5% to about 16% of one or more hydrophilic compounds, for example from about 5% to about 15% of one or more hydrophilic compounds, such as from about 5% to about 14% of one or more hydrophilic compounds, for example from about 5% to about 13% of one or more hydrophilic compounds, such as from about 5% to about 12% of one or more hydrophilic compounds, for example from about 5% to about 11% of one or more hydrophilic compounds, such as about 5% to about 10% of one or more hydrophilic compounds.

In one embodiment the paste according to the invention prior to drying comprises from about 6% to about 40% of one or more hydrophilic compounds, for example from about 6% to about 30% of one or more hydrophilic compounds, such as from about 6% to about 25% of one or more hydrophilic compounds, for example from about 6% to about 20% of one or more hydrophilic compounds, such as from about 6% to about 18% of one or more hydrophilic compounds, for example from about 6% to about 17% of one or more hydrophilic compounds, such as from about 6% to about 16% of one or more hydrophilic compounds, for example from about 6% to about 15% of one or more hydrophilic compounds, such as from about 6% to about 14% of one or more hydrophilic compounds, for example from about 6% to about 13% of one or more hydrophilic compounds, such as from about 6% to about 12% of one or more hydrophilic compounds, for example from about 6% to about 11% of one or more hydrophilic compounds, such as about 6% to about 10% of one or more hydrophilic compounds.

In one embodiment, the paste according to the invention prior to drying comprises more than about 1% of one or more hydrophilic compounds, such as more than about 2% of one or more hydrophilic compounds, for example more than about 3% of one or more hydrophilic compounds, such as more than about 4% of one or more hydrophilic compounds, for example more than about 5% of one or more hydrophilic compounds, such as more than about 6% of one or more hydrophilic compounds, for example more than about 7% of one or more hydrophilic compounds, such as more than about 8% of one or more hydrophilic compounds, for example more than about 9% of one or more hydrophilic compounds, such as more than about 10% of one or more hydrophilic compounds.

After drying, the dry composition comprises from about 10% to about 60% of one or more hydrophilic compounds, such as from about 10% to about 50% of one or more hydrophilic compounds, for example from about 10% to about 50%, such as from about 10% to about 45% of one or more hydrophilic compounds, for example from about 10% to about 40%, such as from about 10% to about 35% of one or more hydrophilic compounds, for example from about 10% to about 30% of one or more hydrophilic compounds.

In one embodiment, the dry composition comprises from about 15% to about 60% of one or more hydrophilic compounds, such as from about 15% to about 50% of one or more hydrophilic compounds, for example from about 15% to about 50%, such as from about 15% to about 45% of one or more hydrophilic compounds, for example from about 15% to about 40%, such as from about 15% to about 35% of one or more hydrophilic compounds, for example from about 15% to about 30% of one or more hydrophilic compounds.

In one embodiment, the dry composition comprises from about 20% to about 60% of one or more hydrophilic compounds, such as from about 20% to about 50% of one or more hydrophilic compounds, for example from about 20% to about 50%, such as from about 20% to about 45% of one or more hydrophilic compounds, for example from about 20% to about 40%, such as from about 20% to about 30% of one or more hydrophilic compounds.

In one embodiment, the dry composition comprises from about 25% to about 60% of one or more hydrophilic compounds, such as from about 25% to about 50% of one or more hydrophilic compounds, for example from about 25% to about 45% of one or more hydrophilic compounds, such as from about 25% to about 40% of one or more hydrophilic compounds, for example from about 25% to about 35% of one or more hydrophilic compounds, such as from about 25% to about 30% of one or more hydrophilic compounds.

In one embodiment, the dry composition comprises less hydrophilic compounds than biocompatible polymer, i.e. the hydrophilic compounds:biocompatible polymer ratio is less than 1:1, such as less than or about 0.9:1, for example less than or about 0.8:1, such as less than or about 0.7:1, for example less than or about 0.6:1, such as less than or about 0.5:1, such as less than or about 0.4:1, for example less than or about 0.3:1, such as less than or about 0.2:1, for example less than or about 0.1:1. The hydrophilic compounds:biocompatible polymer ratio is the same in the paste prior to drying.

In one embodiment, the hydrophilic compounds:biocompatible polymer ratio is between about 0.1:1 and 1:1; such as between about 0.2:1 and 1:1, for example between about 0.3:1 and 1:1, such as between about 0.4:1 and 1:1. In one embodiment, the hydrophilic compounds:biocompatible polymer ratio is between about 0.1:1 and 0.8:1; such as between about 0.1:1 and 0.7:1, for example between about 0.1:1 and 0.6:1, such as between about 0.1:1 and 0.5:1, for example between 0.1:1 and 0.45:1. Even more preferred, the hydrophilic compounds:biocompatible polymer ratio is between about 0.15:1 and 0.8:1; such as between about 0.15:1 and 0.7:1, for example between about 0.15:1 and 0.6:1, such as between about 0.15:1 and 0.5:1, for example between about 0.15:1 and 0.5:1, such as between 0.15:1 and 0.45:1. In a preferred embodiment, the hydrophilic compounds:biocompatible polymer ratio is between about 0.2:1 and 0.8:1; such as between about 0.2:1 and 0.7:1, for example between about 0.2:1 and 0.6:1, such as between about 0.2:1 and 0.5:1, for example 0.2:1 and 0.45:1.

In one embodiment, the hydrophilic compounds:biocompatible polymer ratio is between about 0.3:1 and 0.8:1; such as between about 0.3:1 and 0.7:1, for example between about 0.3:1 and 0.6:1, such as between about 0.3:1 and 0.5:1, for example between about 0.35:1 and 0.5:1, such as between about 0.35:1 and 0.45:1.

In one embodiment the hydrophilic compound is not polyethylene glycol (PEG).

Further Compounds

The dry composition may further comprise one or more of the following: DMSO (dimethyl sulfoxide), 2-Methyl-2,4-pentanediol (MPD) and/or one or more of the compounds mentioned in the table below.

Bulking agent Buffering agent Solubilising agent Miscellaneous Sugars/Sugar Citric acid Complexing agent: Tonicifying agent: alcohols: Sodium citrate Ethylediamine tetra acetic Sodium chloride Mannitol Potassium citrate acid (EDTA) Sucrose Lactose Tartaric acid Alpha cyclodextrin Mannitol Sucrose Sodium phosphate Hydroxypropyl-β- Dextrose Trehalose Tris base cyclodextrin (HP-β-CD) Sorbitol Tris HCl Glucose Tris acetate Raffinose Zinc chloride Sodium acetate Potassium acetate Arginine Amino acids: pH adjusting agent: Surfactants: Antimicrobial Arginine Hydrochloric acid polysorbate 80 agents: Glycine Sodium hydroxide Benzalkonium Histidine Meglumine chloride benzyl alcohol phenol m-cresol methyl paraben ethyl paraben Polymer: Co-solvents: Collapse Dextran Tert-butyl alcohol temperature Polyethylene Iso-propyl alcohol modifier: glycol Dichloromethane Dextran Ethanol Hydroxyethyl starch Acetone Ficoll Glycerol gelatin

In one embodiment, the dry composition comprises one or more antimicrobial agents, such as one or more antibacterial agents.

In one embodiment, the dry composition comprises benzalkonium chloride.

In one embodiment, the dry composition does not comprise an antimicrobial agent.

In one embodiment, the dry composition further comprises an extrusion enhancer, i.e. a compound capable of facilitating extrusion of a paste from a syringe.

It has previously been shown that the provision of certain extrusion enhancers, such as albumin in an appropriate amount, enables the use of higher gelatine concentrations as it decreases the amount of force needed to extrude the gelatine paste composition from e.g. a syringe. The use of higher gelatine concentrations may in turn improve the haemostatic properties of such products. It is necessary to provide the extrusion enhancers in appropriate amounts. The amounts are preferably high enough so as to obtain the extrusion effect, i.e. to enable a flowable paste even for relatively high amounts of the biocompatible polymer, e.g. cross-linked gelatine, so that the haemostatic paste composition can be accurately applied by a surgeon using e.g. a syringe comprising an applicator tip; on the other hand, the amounts shall be as low as to prevent negative functional properties of the haemostatic composition.

The extrusion enhancer is preferably albumin, especially human serum albumin.

In the paste prior to drying, the extrusion enhancer, such as albumin, is preferably present in an amount of between about 0.1% to about 10%, such as between about 0.2% to about 8%, for example between about 0.3% to about 7%, preferably between about 0.5% to about 5%, more preferred between about 1% to about 4%.

In the dry composition, the extrusion enhancer, such as albumin, is preferably present in an amount of between about 0.3% to about 30%, such as between about 0.5% to about 25%, for example between about 1% to about 20%, preferably between about 2% to about 15%.

In one embodiment, the extrusion enhancer is not present in the dry composition, but is instead introduced into the paste composition during reconstitution. For example the extrusion enhancer may be present in the aqueous medium used for reconstitution of the paste, thereby obtaining a wet paste composition comprising the extrusion enhancer. The concentration of the extrusion enhancer in the reconstituted paste will be the same as when the extrusion enhancer is added to the paste prior to drying.

In one embodiment, the reconstituted wet paste compositions according to the present invention have a mean extrusion force (e.g. by employing the test method described in example 1 of WO 2013/060770) of 40 N or below, preferably below 35 N, especially preferred below 30 N or even below 20 N.

Another class of extrusion enhancers according to the present disclosure are phospholipids, such as phosphatidylcholine and -serine, or complex mixtures such as lecithins or soy bean oils.

Bioactive Agent

In one embodiment, the dry composition comprises one or more bioactive agents, i.e. one or more bioactive agents are included in the paste prior to drying. It is essential that the bioactive agent retains its bioactivity throughout the process and that the agent has also retained its biological function in the final reconstituted paste. Many bioactive agents are unstable in solution, particularly enzymes and other proteins that may be degraded or otherwise lose their secondary structure when water is present.

In one embodiment the bioactive agent is thrombin.

In one embodiment the thrombin is human thrombin.

In one embodiment the thrombin is recombinant thrombin.

Conventionally, a thrombin solution is mixed with a dry or pre-wetted gelatine powder to make a haemostatic paste directly at the surgical site at the time of need of the haemostatic paste, e.g. by using commercially available haemostatic kits such as Floseal® and Surgiflo®. The thrombin solution must be made just prior to making the paste as thrombin in solution is very unstable and will self-degrade rapidly. The making of a thrombin solution at the surgical site is time consuming and involves a risk of making mistakes regarding the correct dilution and amount of thrombin.

The present disclosure allows for the addition of thrombin to the paste prior to drying, thereby resulting in a dry haemostatic composition comprising thrombin, which upon reconstitution with a suitable aqueous medium, will comprise a desired amount of thrombin without the need for time-consuming and error-prone thrombin dilution steps and addition at the surgical site. That thrombin may be included in the dry composition of the present disclosure thus constitutes a clear advantage over conventional methods for making haemostatic pastes.

Thrombin may be included in a paste and dried by freeze-drying according to the present disclosure with essentially no loss of thrombin activity measured in the reconstituted paste.

Thrombin may be added to the paste of the present disclosure prior to drying in an amount sufficient to ensure effective haemostasis of the reconstituted dry composition. In one embodiment thrombin is added at a concentration in the range of about 100 IU/ml paste to about 500 IU/ml paste, such as about 150 IU/ml paste to about 450 IU/ml paste, for example about 200 IU/ml paste to about 400 IU/ml paste, such as about 250 IU/ml paste to about 350 IU/ml paste.

In one embodiment, thrombin is added to the paste prior to drying at a concentration in the range of about 50 IU/g paste to about 5000 IU/g paste, preferably between about 100 IU/g paste to about 1000 IU/g paste, such as between about 200 IU/g paste to about 800 IU/g paste. In such embodiments, the dry composition will comprise thrombin.

In other embodiments, the dry composition does not comprise thrombin and thrombin may be added upon reconstitution of the dry composition by reconstituting the dry paste composition with a liquid comprising thrombin.

The one or more bioactive agents can be e.g. thrombin or thrombin in combination with fibrinogen, or thrombin and fibrinogen in combination with Factor XIII, or thrombin and fibrinogen and Factor XIII in combination with tranexamic acid.

Thrombin is a “trypsin-like” serine protease protein that in humans is encoded by the F2 gene. Prothrombin (coagulation factor II) is proteolytically cleaved to form thrombin in the coagulation cascade, which ultimately results in the stemming of blood loss. Thrombin in turn acts as a serine protease that converts soluble fibrinogen into insoluble strands of fibrin, as well as catalyzing many other coagulation-related reactions. In the blood coagulation pathway, thrombin acts to convert factor XI to XIa, VIII to VIIIa, V to Va, and fibrinogen to fibrin.

A preferred bioactive agent according to the invention is thrombin. In one embodiment, the thrombin is added as prothrombin.

In one embodiment, the dry composition comprises one or more bioactive agents that stimulate bone and/or tendon and/or tissue healing such as one or more growth factors selected from the group consisting of matrix metalloproteinases (MMPs), insulin-like growth factor 1 (IGF-I), platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and transforming growth factor beta (TGF-β).

In one embodiment, the dry composition comprises one or more Bone Morphogenetic Proteins (BMPs). Bone morphogenetic proteins (BMPs) are a subgroup of the TGF-β superfamily. Bone Morphogenetic Proteins (BMPs) are a group of growth factors also known as cytokines and as metabologens. Originally discovered by their ability to induce the formation of bone and cartilage, BMPs are now considered to constitute a group of pivotal morphogenetic signals, orchestrating tissue architecture throughout the body.

In one embodiment, the dry composition of the present disclosure comprises one or more matrix metalloproteinases (MMPs). MMPs are zinc-dependent endopeptidases. MMPs have a very important role in the degradation and remodeling of the extracellular matrix (ECM) during the healing process after an injury. Certain MMPs including MMP-1, MMP-2, MMP-8, MMP-13, and MMP-14 have collagenase activity, meaning that, unlike many other enzymes, they are capable of degrading collagen I fibrils.

These growth factors all have different roles during the healing process. IGF-1 increases collagen and proteoglycan production during the first stage of inflammation, and PDGF is also present during the early stages after injury and promotes the synthesis of other growth factors along with the synthesis of DNA and the proliferation of cells. The three isoforms of TGF-β (TGF-β1, TGF-β2, TGF-β3) are known to play a role in wound healing and scar formation. VEGF is well known to promote angiogenesis and to induce endothelial cell proliferation and migration.

In one embodiment, the dry composition of the present disclosure comprises flakes or particles of extracelluar matrix (ECM). ECM is the extracellular part of animal tissue that usually provides structural support to the animal cells in addition to performing various other important functions. ECM has been shown to have very beneficial effect in healing as it facilitates functional tissue regeneration.

The variety of biological agents that can be used in conjunction with the paste of the invention is vast. In general, biological agents which may be administered via compositions of the present disclosure include, without limitation, antiinfectives, such as antibiotics and antiviral agents; analgesics and analgesic combinations; antihelmintics; antiarthritics; anticonvulsants; antidepressants; antihistamines; antiinflammatory agents; antimigraine preparations; antineoplastics; antiparkinsonism drugs; antipsychotics; antipyretics, antispasmodics; anticholinergics; sympathomimetics; xanthine derivatives; cardiovascular preparations including calcium channel blockers and beta-blockers such as pindolol and antiarrhythmics; antihypertensives; diuretics; vasodilators, including general coronary, peripheral and cerebral; central nervous system stimulants; hormones, such as estradiol and other steroids, including corticosteroids; immunosuppressives; muscle relaxants; parasympatholytics; psychostimulants; naturally derived or genetically engineered proteins, polysaccharides, glycoproteins, or lipoproteins; oligonucleotides, antibodies, antigens, cholinergics, chemotherapeutics, radioactive agents, osteoinductive agents, cystostatics heparin neutralizers, procoagulants and haemostatic agents, such as prothrombin, thrombin, fibrinogen, fibrin, fibronectin, heparinase, Factor X/Xa, Factor VII/VIIa, Factor VIII/VIIIa, Factor IX/IXa, Factor XI/XIa, Factor XII/XIIa, Factor XIII/XIIIa, tissue factor, batroxobin, ancrod, ecarin, von Willebrand Factor, collagen, elastin, albumin, gelatin, platelet surface glycoproteins, vasopressin, vasopressin analogs, epinephrine, selectin, procoagulant venom, plasminogen activator inhibitor, platelet activating agents and synthetic peptides having haemostatic activity.

Making the Paste

According to the method of the invention, the biocompatible polymer in powder form and the alkaline compound are mixed with a suitable amount of an aqueous medium to obtain a paste, which is subsequently dried. Alternatively, the biocompatible polymer in powder form is mixed with an acidic compound in the presence of a suitable amount of an aqueous medium to obtain a paste and the paste is subsequently dried. The mixing is performed under conditions effective to provide a substantially homogeneous paste composition and may be performed in any suitable way known to a person of skill, e.g. by mixing the contents manually or by using an electrical mixing apparatus, such as a hand mixer, a kitchen mixer or an industrial mixer.

The powder particles of the biocompatible polymer are usually substantially insoluble in the aqueous medium allowing for a paste to form. Cross-linking generally renders biocompatible polymers, such as gelatine, insoluble in water.

Mixing of the paste in the mixing vessel introduces a discontinuous gas phase substantially homogenously dispersed through the paste, i.e. the mixed paste will comprise pockets or isolated bodies of gas, such as air.

In one embodiment, the paste is made by mixing an aqueous medium, a gas and an amount of powder particles in a mixing vessel under conditions resulting in the formation of a paste having a discontinuous gas phase substantially homogenously dispersed through the paste. The gas may for example be air, nitrogen, carbon dioxide, xenon, argon or mixtures thereof.

In a particular embodiment, the paste is prepared by the following steps:

-   -   introducing a volume of a liquid into a mixing vessel equipped         with a means for mixing said liquid,     -   introducing a volume of a gas into said volume of liquid while         said means for mixing is operating under conditions effective to         mix said liquid and said gas together to form a foam comprising         a discontinuous gas phase comprising said gas dispersed in a         continuous liquid phase comprising said liquid,     -   introducing into said foam an amount of powder particles of a         biocompatible polymer suitable for use in hemostasis and which         is substantially insoluble in said liquid; and     -   mixing said foam and said powder particles together under         conditions effective to form a substantially homogenous paste         composition comprising said discontinuous gas phase and said         particles substantially homogenously dispersed throughout said         liquid phase, thereby forming a paste composition.

In one embodiment, the substantially homogenous paste composition comprises a continuous liquid phase, i.e. a liquid phase which can be released when applying force to the paste when the paste is contained in an enclosed space.

In one embodiment, the powder particles comprise pores and channels of a size sufficient to hold water by capillary forces. When a paste is made using such particles, water can be released from the paste upon application of force to the paste when the paste is contained in a confined space.

The obtained paste is then transferred into a container suitable for vacuum expansion, freezing and drying of the paste. Preferably, the container into which the paste is transferred is also suitable for reconstituting and applying the reconstituted paste composition, e.g. to a site requiring hemostasis.

The mixing of the paste can generally be performed at room temperature (20-25° C.). However, if thrombin or other sensitive agents, such as other enzymes are included in the paste, it is advisable to perform the mixing of the paste at chilled temperatures and/or within a short time period to avoid or decrease the proteolytic activity of thrombin, as it is well-known that thrombin is liable to self-degradation when wet. Hence, when thrombin or other sensitive bioactive agents are to be included in the paste, the mixing of the paste is usually performed at temperatures below room temperature, such as at about 2° C. to about 25° C., for example at about 2° C. to about 15° C., such as about 2° C. to about 10° C., preferably at about 4° C.

Another or an additional way of preserving the thrombin bioactivity in the paste is to keep the time that thrombin is in a wet state, i.e. the mixing time, at a minimum. Hence, when thrombin or other proteolytic enzymes are to be included in the paste, the mixing of the paste is usually performed within about 5 minutes to about 10 hours, such as about 5 minutes to about 5 hours, for example about 5 minutes to about 2 hours, preferably about 5 minutes to about 1 hour, such as within about 5 minutes to about 30 minutes.

It is not essential to perform the mixing of the paste at low temperatures to avoid loss of thrombin activity as no detectable decrease in thrombin activity was discovered when mixing of the paste was performed at ambient temperatures (Example 2).

The density of the wet paste is usually in the range of about 0.5 g/ml to about 1 g/ml, such as between about 0.6 g/ml to about 0.9 g/ml, for example between about 0.7 g/ml to about 0.8 g/ml.

Containers

Any suitable container known to a person of skill may be used for preparing the paste and holding the paste of the present disclosure while drying, such as vials, jars, tubes, trays, cartridges or syringes.

In one embodiment, the paste is prepared in one container in bulk, such as in a large mixing bowl, and transferred/aliquoted into another container for drying, wherein said other container is selected from an applicator, such as a syringe, a vial, a jar, a tube, a tray and a cartridge. Preferably, the other container is a medical delivery device suitable for dispensing flowable haemostatic compositions to a patient in need thereof.

In one embodiment the container holding the paste composition during drying is an applicator, such as a syringe.

A “jar” according to the invention is a rigid, approximately cylindrical container with a wide mouth opening. Jars may comprise a re-closable closure unit/lid applied to the mouth of the jar.

The containers may be made from any suitable material such as plastic, glass, ceramic or metal, such as stainless steel.

Examples of suitable plastic materials include but are not limited to polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polytetrafluoroethylene (PTFE).

In one embodiment, the paste is filled into and dried within an applicator suitable for dispensing flowable haemostatic compositions.

In one embodiment, the present disclosure relates to a container comprising:

-   -   a) a product chamber comprising the dry composition according to         the present disclosure, and     -   b) a valve.

In one embodiment, the container of the present disclosure is a partial syringe assembly comprising the dry composition as defined herein and a valve.

Preferably, the dry composition reconstitutes spontaneously to form a flowable paste upon addition of an aqueous medium to the dry composition being present in the container.

In one embodiment, the pressure within the product chamber is less than the pressure outside the product chamber.

In one embodiment, the container comprises a bypass allowing for gaseous communication between the product chamber and the outside of the container during drying.

Gaseous communication during vacuum expansion and drying can also occur through the valve in embodiments of the present disclosure involving vacuum expansion of the paste when the container does not comprise a bypass.

The dry composition of the present disclosure may be prepared in various shapes, forms and sizes depending on the shape of the container used. They may be e.g. in the form of plugs, disks, rods, tubes, conical cylinders, spheres, half spheres, tablets, pellets, granules or sheets.

In one embodiment, the container is a medical delivery device.

Medical Delivery Device

In one embodiment, the paste is filled into and dried within a medical delivery device suitable for dispensing flowable haemostatic compositions, such as a syringe. The transfer takes place before drying of the paste. In embodiments of the present disclosure involving vacuum expansion of the paste prior to drying, the transfer takes place before vacuum expansion.

In one embodiment, the medical delivery device is a single-use syringe comprising a valve. In one embodiment, the syringe comprises a lyophilisation bypass channel being a gaseous communication between the product chamber of the syringe and the outside of the container, i.e. the external environment. The bypass may be in an open state allowing for gaseous communication between the product chamber and the outside, and in a closed state. The bypass may be located anywhere allowing for gaseous communication between the product chamber and the external environment e.g. in the syringe body or in the plunger as shown in FIG. 5. If the syringe comprises a bypass in the syringe body (FIG. 5, concept 2), the syringe may be fitted with a standard plunger.

One embodiment of the present disclosure relates to a syringe for retaining a freeze-dried paste, such as the presently disclosed dry composition, in a vacuum comprising a barrel comprising a vacuum chamber for containing the paste having an open proximal end and a distal end having a first fluid opening, a connector portion having a second fluid opening and adapted for connection to a liquid receptacle, and a pressure chamber connecting the connector portion and the distal end of the vacuum chamber, a pressure valve located in the pressure chamber and adapted to seal the first and/or second fluid openings in a first position and form a fluid passageway between the first and second fluid openings in a second position, a plunger configured to be axially displaced in the vacuum chamber through the open proximal end, and optionally one or more vacuum bypass channels. The syringe is preferably a single-use disposable syringe.

When freeze-drying the paste the vacuum that can be created in the vacuum chamber can be used to expand the paste prior to drying. And by retaining the dry paste in a vacuum in the vacuum chamber of the syringe, i.e. at a pressure level lower than the surrounding ambient pressure, addition of liquid upon preparation and use of the paste is eased, because the liquid is sucked into the vacuum chamber due to the reduced pressure in the vacuum chamber.

The barrel may be provided with a flange at the proximal end of the vacuum chamber in order to ease handling of the syringe when operating the plunger. Furthermore, the inside volume of the vacuum chamber and/or the pressure chamber may advantageously be cylindrical.

The connector portion may be a connector portion of a standard type, such as a Luer lock or Luer slip connector, preferably a male Luer lock or Luer slip connector. The connector portion may be provided with a threaded portion for secure connection with matching connector. This threaded portion may be provided at the inside of the connector portion as illustrated in FIGS. 18a, 18b, 20a and 20 b.

In one embodiment of the presently disclosed syringe the pressure valve comprises a groove. This groove may form the fluid passageway in the second position of the pressure valve. One example is illustrated in FIGS. 18a and 18b . As also illustrated in FIGS. 18a and 18b the pressure valve 5 may comprise two cylindrical sections axially divided by a groove 12, and wherein the void formed by the groove 12 forms the fluid passageway in the second position of the pressure valve 5. In this configuration the pressure valve may be rotation symmetric along the longitudinal axis of the pressure valve as seen from FIG. 18, i.e. the pressure valve may be rotated inside the pressure chamber without interfering with the function of the pressure valve, i.e. in the first position of the pressure valve the vacuum chamber is sealed independent of the rotational position of the pressure valve, and in the second position of the pressure valve a fluid connection is formed between the vacuum chamber and the connector portion independent of the rotational position of the pressure valve.

The pressure valve may be provided in a rubbery material and/or with a rubbery surface to provide for the sealing of the first and second fluid openings in the first position of the pressure valve.

The pressure chamber is preferably located between the vacuum chamber and the second fluid opening. Furthermore, the pressure valve is preferably located in the pressure chamber and adapted to seal the first and second fluid openings in a first position in the pressure chamber and form/create a fluid passageway between the first and second fluid openings in a second position in the pressure chamber, e.g. the pressure valve is preferably located in the pressure chamber, e.g. inside the pressure chamber, in both the first and second positions. I.e. preferably the pressure valve stays inside the pressure chamber during control of the fluid passage between the first and second fluid openings.

In one embodiment of the presently disclosed syringe the pressure chamber comprises a proximal end abutting the distal end of the vacuum chamber and a distal end abutting a proximal end of the connector portion. Further, the connector portion may comprise a proximal end abutting a distal end of the pressure chamber and a distal end adapted for connection to a liquid receptacle. The second fluid opening may form an elongated channel through the connector portion, e.g. as illustrated in FIGS. 18 and 20. As also seen from these figures the second fluid opening may comprise a proximal end abutting a distal end of the pressure chamber and a distal end for inlet and outlet of fluid. Hence, the pressure valve may be adapted to seal a distal end of the first fluid opening and a proximal end of the second fluid opening in said first position.

Thus, with the presently disclosed syringe the liquid for reconstitution of a dry composition in the vacuum chamber to obtain a paste can be provided from the distal end of the syringe, via the second fluid opening in the connector portion and through the pressure chamber and into the vacuum chamber. Delivery of the reconstituted paste is also provided through the distal end of the syringe. This solution is possible because of the provision of the dedicated pressure chamber with the pressure valve located between the vacuum chamber and the distal fluid opening, whereby it may be possible to control the blockage and opening of the fluid passageway between the first and second fluid openings without removing the pressure valve from the pressure chamber and also without access to the second fluid opening. Thus, an external liquid receptacle may be connected to the connector portion of the syringe while the pressure valve is in the first position, i.e. the fluid passageway is blocked (sealed). Switching the pressure valve to the second position opens the fluid passageway and liquid can pass from the liquid receptacle to the vacuum chamber of the syringe for reconstitution of the dry composition. The presently disclosed syringe is therefore safe, easy and quick to use when reconstituting a dry paste composition, such as a haemostatic paste.

In a further embodiment of the presently disclosed syringe the first and second positions of the pressure valve are radially displaced with respect to the longitudinal axis of the syringe. Furthermore, the pressure valve may protrude from the pressure chamber in the first position of the pressure valve. And further, the pressure valve may be flush with the pressure chamber in the second position of the pressure valve, e.g. fully incorporated in the pressure chamber. The pressure valve may be provided with a valve flange at an end of the pressure valve protruding from the pressure chamber. This valve flange may protrude from the pressure chamber in said first position, and the valve flange may be flush with the pressure chamber in said second position. The valve flange may then have the function as a stop flange for the pressure valve, i.e. the pressure valve may be configured such that the valve flange abuts the pressure chamber in the second position of the pressure valve.

In yet another embodiment of the presently disclosed syringe the first and second positions of the pressure valve are rotatably displaced, e.g. as illustrated in FIGS. 3-13, with the closed position in FIGS. 3-12 and the open position in FIG. 13. As also exemplified in these figures the pressure valve may comprise a through-going channel forming the fluid passageway in the second position of the pressure valve. Furthermore the pressure valve may comprise a cylindrical section with a through-going radial channel forming the fluid passageway in the second position of the pressure valve.

In a further embodiment the pressure valve and the pressure chamber are configured such that the second position of the pressure valve is a locked position. The pressure valve may be axially and/or rotatably locked in this locked position. This may help to ensure that once the pressure valve has been moved to the second position, it stays there, thereby ensuring that paste can be expelled from the syringe when needed. The pressure valve and the pressure chamber may further be configured such the first position is a partly locked position, e.g. the pressure valve cannot be removed from/out of the pressure chamber but can only be moved into the second position. This may help to ensure that the vacuum is retained inside the vacuum chamber.

In a further embodiment of the presently disclosed syringe the pressure valve comprises an aperture, and this aperture preferably forms at least a part of the fluid passageway in the second position of the pressure valve. I.e. preferably this aperture extends transversally through the pressure valve such that the aperture extends in the longitudinal direction of the barrel when inserted in the pressure chamber.

In a further embodiment the pressure valve and the pressure chamber are configured such that the pressure valve is radially limited in said first position, such as radially limited outwards with respect to the longitudinal axis of the barrel. This radial limitation may be provided by means of one or more protrusions on the pressure valve and/or inside the pressure chamber. E.g. the pressure valve comprises one or more protrusions, preferably extending sideways, such as radial to the fluid passageway. The limitation may also be provided by means of a narrowing of an inner side wall of the pressure chamber and this narrowing may be adapted to limit a radial displacement of the pressure valve in the first position, e.g. this narrowing may be adapted to match one or more protrusions of the pressure valve, such that this or these protrusions abuts the narrowing in the first position of the pressure valve. A narrowing may be provided by means of one or more “shoulders” of an inner side wall of the pressure chamber, as exemplary illustrated in FIGS. 19c and 19 d.

In a further embodiment the pressure valve protrudes transversely and/or radially from the pressure chamber in said first position and wherein the pressure valve is flush with or totally submerged into the pressure chamber in said second position. The pressure valve may be provided with a top surface, wherein said top surface may be flush with a top surface of the pressure chamber in said first position. These top surfaces may be rounded and/or matched to each other as illustrated in FIGS. 19 and 20.

The pressure valve and the pressure chamber may be configured such that the pressure valve can be inserted from one side of the pressure chamber, such as through only one side of the pressure chamber, e.g. through an opening of the pressure chamber, e.g. a bottom opening of the pressure chamber where a top opening of the pressure chamber may be where through the pressure valve extends when in the first position.

The presently disclosed syringe is preferably configured such that a paste composition may be freeze-dried inside the vacuum chamber. The one or more vacuum bypass channels may be configured to provide a fluid, such as a gaseous, communication between the vacuum chamber and the surroundings/the ambient atmosphere, i.e. the vacuum bypass channel(s) may function as the lyophilisation bypass channel as described herein. In one embodiment the syringe is configured such that the plunger sealably engages the vacuum chamber in at least a first axial position of the plunger inside the vacuum chamber, and such that fluid communication is established across the plunger in at least a second axial position of the plunger inside the vacuum chamber via said one or more vacuum bypass channels. I.e. a vacuum can be established and the composition can be freeze-dried in the second position of the plunger, whereas the vacuum in the vacuum chamber can be retained in the first position of the plunger. However, alternatively said one or more vacuum bypass channels are configured such that a fluid communication can be provided directly between the vacuum chamber and the ambient atmosphere independent of the position of the plunger, e.g. via a (second) pressure valve located directly at the vacuum chamber. Alternatively said one or more vacuum bypass channels may be formed in the plunger.

Hence, the one or more vacuum bypass channels may be configured to break the sealing between the vacuum chamber and the plunger at a predefined axial position of the plunger inside the vacuum chamber. Furthermore, said one or more vacuum bypass channels may be formed in the vacuum chamber. E.g. said one or more vacuum bypass channels may be one or more longitudinal grooves formed in the inner surface, e.g. at the proximal end of the vacuum chamber.

In one embodiment of the presently disclosed syringe the barrel is formed in a single piece of material. The barrel may advantageously be suitable and/or adapted for manufacture by means of single cycle injection moulding, i.e. the barrel may advantageously be manufactured by means of single cycle injection moulding. I.e. the vacuum chamber, the pressure chamber and the connector portion may be integrated and/or incorporated to form a single element, e.g. as illustrated in FIGS. 16-18. This may help to ensure that a vacuum can be established and retained inside the vacuum chamber.

However, alternatively the vacuum chamber, the pressure chamber and the connector portion may be formed as separate elements and configured to be assembled during manufacture of the syringe.

Further, the pressure chamber and the connector portion may be formed as one element and configured to be assembled with the vacuum chamber during manufacture of the syringe. Alternatively the vacuum chamber and the pressure chamber may be formed as one element and configured to be assembled with the connector portion during manufacture of the syringe.

A barrel 1, 1′ of the presently disclosed syringe is exemplified in FIGS. 16-18. The barrel 1 in FIG. 16a is provided with a vacuum chamber, a pressure chamber 3, a connector portion 4 and a flange 8 formed in a single piece and suitable for manufacture by single cycle injection moulding. The pressure valve 5 inserted in the pressure chamber 3 is provided with a valve flange 6. In FIG. 16a the pressure valve is located in a first position whereas in FIG. 16b the pressure valve has been displaced to a second position. This is more clearly seen in FIGS. 16c (first position of pressure valve) and 16 d (second position). In the second position of the pressure valve 5 the valve flange 6 abuts the pressure chamber 3.

The cut-through illustrations in FIGS. 18a and 18b more clearly shows the configuration of the pressure valve 5. In the first position in FIG. 18a the pressure valve blocks the fluid communication between the outlet 11 of the internal volume 2′ of vacuum chamber 2 and the outlet 7 of the connector portion 4. In the second position of the pressure valve 5 in FIG. 18b a fluid communication is provided (as illustrated by the dotted line/arrow) between the surroundings and the internal volume 2′ of the vacuum chamber 2 via the pressure chamber 3 and the outlet 7 of the connector portion 4, i.e. liquid can enter the vacuum chamber 2′ to mix with a dry composition, e.g. to form a wet paste that subsequently can be controllably released via the outlet 7 by operating a plunger (not shown) arranged in the barrel 1, 1′. The barrel 1′ in FIG. 17a does not have a flange.

As seen from FIG. 18 the pressure valve 5 is formed like a cylinder with a circumferential groove 12 that forms the fluid opening in the second position of the pressure valve. I.e. the pressure valve 5 is formed like two hollow cylinders that are attached to each other by means of the centrally located rod 13. Even though the rod 13 is located centrally in the fluid passageway, liquid that enters the vacuum chamber 2 via the outlet 7, and paste that is released from the barrel 1, 1′ through the outlet 7 can easily pass the rod 13. The pressure valve 5 as illustrated in FIG. 18 is rotation symmetric.

The connector portion 4 is provided with an internal thread 10, most clearly seen in FIG. 18. This may help to provide a secure, tight and tamper-free connection with an external liquid container (having a connector portion with a matching thread) prior to suction of liquid into the vacuum chamber when the (wet) paste is to be formed.

Vacuum bypass channels 9 are provided in FIGS. 16-18 as longitudinally extending grooves in the proximal end of the vacuum chamber 2. When the plunger (not shown) is arranged in the barrel 1, 1′ below these vacuum channels the plunger sealably engages the vacuum chamber. However, when the distal part of the plunger is flush with the bypass vacuum channels 9, this sealing is not tight, because a fluid, and in particular air, connection is established between the vacuum chamber 2′ and the surrounding atmosphere across the plunger via the vacuum bypass channels 9. I.e. during free-drying of paste inside the vacuum chamber 2′ suction applied at the proximal end of the barrel can establish a vacuum inside the pressure chamber 2′ and thereby expand the dry paste. At the end of the freeze-drying and expansion process, the plunger can be displaced to a position below the vacuum bypass channels, thereby sealably engaging the vacuum chamber 2 and subsequently retaining the freeze-dried paste in a vacuum.

Another exemplary barrel 1″ of the presently disclosed syringe is exemplified in FIG. 20 having another embodiment of the pressure valve 5′ and the pressure chamber 3′ as illustrated in greater detail in FIG. 19, with FIG. 19a showing a close-up of the pressure valve alone. This pressure valve 5′ is slim and provided in a substantially rectangular shape. An aperture 17 forms the fluid passageway in the second position of pressure valve inside the pressure chamber 3′. The outside shape of the pressure valve 5′ matches the inside shape of the pressure chamber 3′. FIG. 19b shows the pressure valve 5′ inside the pressure chamber 3′ in the first position of the pressure valve 5′, where the fluid passageway is blocked and a vacuum can be retained inside the vacuum chamber 2. In FIG. 19b the pressure valve 5′ is seen to protrude upwards from the pressure chamber 3′, i.e. it protrudes radially from the pressure chamber 3′ with respect to the longitudinal axis of the barrel 2. In FIGS. 19c and 19d the pressure chamber 3′ has been cut-through such that the configuration of the pressure valve 5′ inside the pressure chamber 3′ can be seen. In FIG. 19c the pressure valve 5′ is in the first position, i.e. extending radially from the pressure chamber 3′. The pressure valve 5′ and the pressure chamber 3′ are configured such that the pressure valve is radially limited in this first position by means of protrusions 14 on the pressure valve 5′ that abuts a narrowing 15 of the inner side wall of the pressure chamber 3′, i.e. the pressure valve 5′ cannot extend further outwards when in the first position. This helps to ensure that the pressure valve 5′ is not accidentally removed from the pressure chamber 3′ thereby possibly breaking a vacuum sealing inside the vacuum chamber 2. In FIG. 19d the pressure valve 5′ is in the second position. The pressure valve 5′ is now completely submerged in the pressure chamber 3′. The rounded top surface of the pressure valve 5′ matches a corresponding rounded top surface of the pressure chamber 3′ such that the upper surfaces of the pressure valve 5′ and the pressure chamber 3′ are flush with each other.

FIGS. 20a-b show cut-through side view illustrations of the pressure valve 5′ inside the pressure chamber 3′ with the first position of the pressure valve in FIG. 20a and the second position in FIG. 20b . As seen in FIG. 20a the fluid passageway 7 is blocked by the pressure valve 5′, whereas in FIG. 20b the aperture 17 of the pressure valve 5′ establishes a fluid connection as indicated by the stippled horizontal arrow in FIG. 20b . FIG. 20b also illustrates how the pressure valve 5′ does not protrude from the pressure chamber 3′ in this second position. This helps to ensure that once the fluid passageway has been established by the pressure valve 5′ in the second position, the position of the pressure valve 5′ is not easily changed because it is submerged inside the pressure chamber 3′.

A stippled arrow in FIG. 20a indicates the opening 16 where through the pressure valve 5′ can be inserted into the pressure chamber 3′. The barrel 1″ is also suitable for single cycle injection molding. After manufacture the pressure valve 5′ can be inserted through the opening 16. The pressure valve 5′ in itself is also suitable for single cycle injection molding. The three top holes 18 indicated in FIGS. 19a and 20c are provided to make the pressure valve 5′ suitable for injection molding.

Haemostatic Sheet

In one embodiment the dry composition is in the form of a sheet, i.e. a substantially flat composition.

A dry composition in the form of a sheet may be obtained by spreading the paste of the invention thinly and evenly on a surface and drying of the paste to obtain a substantially flat dry sheet composition. A dry composition in the form of a sheet will upon contact with a liquid reconstitute spontaneously to form a paste. Thus, a dry composition in the form of a sheet has the advantages of both traditionally used surgical sponges in that it can cover relatively large areas and the advantage of a paste in that it conforms easily to uneven surfaces upon wetting.

The dry composition in the form of a sheet is soft and flexible.

In one embodiment the invention relates to a dry composition in the form of a sheet for use in haemostasis and/or wound healing.

In one embodiment, the sheet is not pre-wetted before use, i.e. before application to a wound. In this case, the sheet will reconstitute in situ on the bleeding wound upon contact with blood, wound exudate, and/or other bodily fluids.

The height of the dry sheet composition is in one embodiment between about 0.5 mm and about 10 mm, preferably between about 1 mm and 5 mm, more preferred between about 1 mm and 3 mm, such as about 2 mm.

The size (width and depth) of the dry sheet composition depends on the intended use of the sheet and can be selected by the skilled person. The dry sheet material may e.g. be rectangular, square or circular. For example, the dry sheet composition may e.g. be in the form of a rectangle of approximately 5 cm×10 cm, 2 cm×6 cm, 6 cm×8 cm or 8 cm×12 cm.

The dry sheet composition can be cut into any desired shape prior to use.

Vacuum Expansion

In one embodiment of the present disclosure, the paste is expanded by subjecting the paste to a reduced pressure (a low vacuum) before the paste is dried. Vacuum expansion results in an increase in the total volume of the paste by expansion of entrapped air or another gas within interstitial pores or compartments of the wet paste. Vacuum expansion of a paste prior to drying significantly decreases the reconstitution time of the dried paste. For example, a vacuum expanded, dry gelatine paste composition being present in a medical delivery device will reconstitute within seconds to a ready-to-use paste suitable for direct delivery to a patient without any mechanical mixing required upon addition of an amount of an aqueous medium to the medical delivery device having the dry gelatine paste composition disposed therein.

Vacuum expansion expands entrapped air pockets within the paste and such expanded air pockets are retained in the dry composition. The presence of larger air pockets in the dry composition presumably enables the wetting of the dry composition due to a larger contact surface area between the dry composition and the liquid. It also facilitates unhindered distribution of the liquid into the dry composition due to the formed channels.

The inventors have also discovered that the volume of a paste aliquot is generally higher in samples being aliquoted first as opposed to last from a single batch of paste. This is thought to be due to a partial collapse of the paste occurring over time causing variations in paste density before drying. Such variations in density can lead to undesirable variations in the reconstitution time. Vacuum expansion of the paste prior to drying is able to reduce or even eliminate such “intra-batch” variations in paste density and thus lead to consistently fast reconstitution of the dried pastes. Thus, vacuum expansion provides a higher degree of reproducibility with regards to the reconstitution time.

The pressure of the vacuum is selected so that the paste expands to a sufficient degree without collapsing. Thus, the pressure must not be too low, which will result in the paste collapsing. Vacuum expansion of the paste may e.g. be performed in a freeze-dryer.

Vacuum expansion of the paste is a result of one of the universal laws of physics: the ideal gas law, which governs that the volume of a gas will increase upon a decrease in pressure. The ideal gas law equation is: PV=nRT where P is the pressure of the gas, V is the volume of the gas, n is the amount of substance of gas (in moles), T is the temperature of the gas and R is the ideal, or universal, gas constant.

Subjecting a wet paste to a sub-atmospheric pressure results in an expansion of the air or other gas within the interstitial spaces (pores) of the paste, which in turn leads to an increase in the total volume of the paste and a decrease in the density of the paste. After drying of the paste composition to achieve a dry paste composition, the increased pore size results in increased permeability and wettability and thus an increased reconstitution rate of the dry composition. Thus, in one embodiment, the present disclosure relates to a method for adapting paste volume by adjusting paste density by subjecting a wet paste to a reduced pressure.

In one embodiment the density of the paste is decreased by at least a factor 0.95 as a result of the vacuum expansion, such as at least a factor 0.90, for example at least a factor 0.85, such as at least a factor 0.80, for example at least a factor 0.75, such as at least a factor 0.70, for example at least a factor 0.65, such as at least a factor 0.60, for example at least a factor 0.55, such as at least a factor 0.50 as a result of the vacuum expansion. Preferably, the density of the paste is decreased by at least a factor 0.8 as a result of the vacuum expansion.

In one embodiment the density of the paste is decreased by about a factor 0.75 as a result of the vacuum expansion.

Prior to vacuum expansion of the paste, the density of the wet paste may e.g. be in the range of about 0.5 g/ml to about 1 g/ml, such as between about 0.6 g/ml to about 0.9 g/ml, for example between about 0.7 g/ml to about 0.8 g/ml.

For example, the density of a gelatine paste prior to expansion is usually within the range of about 0.60 g/ml to about 0.80 g/ml, such as about 0.65 g/ml to about 0.75 g/ml, such as about 0.7 g/ml.

The density of the wet paste after vacuum expansion is less than the density of the wet paste before vacuum expansion. For example, the density of the wet paste after vacuum expansion may e.g. be in the range of about 0.1 g/ml to about 0.8 g/ml, more preferred between about 0.2 g/ml to about 0.7 g/ml, for example about 0.2 g/ml to about 0.6 g/ml, such as about 0.2 g/ml to about 0.5 g/ml.

For example, the density of a gelatine paste after expansion is usually within the range of about 0.2 g/ml to about 0.6 g/ml, more preferred between about 0.3 g/ml to about 0.6 g/ml, such as between about 0.4 g/ml to about 0.5 g/ml.

The volume of the paste, by subjecting the paste to a reduced pressure, is approximately increased by at least about a factor 1.05, such as at least a factor 1.1, for example at least a factor 1.2, such as at least a factor 1.3, for example at least a factor 1.4, such as at least a factor 1.5, for example at least a factor 1.6, such as at least a factor 1.7, for example at least a factor 1.8, such as at least a factor 1.9, for example at least a factor 2.0.

In one embodiment, the volume of the paste is increased by from about a factor 1.05 to about a factor 2.0, such as about a factor 1.1 to about a factor 1.8, for example about a factor 1.2 to about a factor 1.6 as a result of the vacuum expansion of the wet paste.

After drying, the density of the dried paste composition is further decreased due to removal of the water. After drying of the vacuum expanded wet paste, the density of the dry paste composition is thus usually within the range of about 0.1 mg/ml to about 100 mg/ml, more preferred between about 1 mg/ml to about 50 mg/ml, such as between about 5 mg/ml to about 40 mg/ml.

For example, a dry vacuum expanded composition comprising gelatine prepared by the method of the present disclosure usually has a density of between about 1 mg/ml to about 40 mg/ml, such as between about 5 mg/ml to about 35 mg/ml, for example between about 10 mg/ml to about 35 mg/ml.

In one embodiment, the density of the vacuum expanded dry composition is within the range of about 1 mg/ml to about 40 mg/ml, more preferred between about 5 mg/ml to about 40 mg/ml, such as between about 5 mg/ml to about 38 mg/ml, for example between about 5 mg/ml to about 36 mg/ml, such as between about 5 mg/ml to about 34 mg/ml, for example between about 5 mg/ml to about 32 mg/ml, such as between about 5 mg/ml to about 30 mg/ml, for example between about 5 mg/ml to about 28 mg/ml, such as between about 5 mg/ml to about 26 mg/ml, for example between about 5 mg/ml to about 24 mg/ml, such as between about 5 mg/ml to about 22 mg/ml, for example between about 5 mg/ml to about 20 mg/ml.

In one embodiment, the paste is subjected to a reduced pressure of at least 10 mbar less than ambient pressure, for example at least 50 mbar less than ambient pressure, such as at least 100 mbar less than ambient pressure, for example at least 150 mbar less than ambient pressure, such as at least 200 mbar less than ambient pressure, for example at least 250 mbar less than ambient pressure, such as at least 300 mbar less than ambient pressure, for example at least 350 mbar less than ambient pressure, such as at least 400 mbar less than ambient pressure, for example at least 450 mbar less ambient pressure, such as at least 500 mbar less than ambient pressure, for example at least 550 mbar less ambient pressure, such as at least 600 mbar less than ambient pressure, for example at least 650 mbar less ambient pressure, such as at least 700 mbar less than ambient pressure, for example at least 750 mbar less than ambient pressure, such as at least 800 mbar less than ambient pressure, for example at least 850 mbar less than ambient pressure, such as at least 900 mbar less ambient pressure.

The pressure of the vacuum is preferably selected so that the pressure is at least 50 mbar less than ambient pressure but no more than 900 mbar less than ambient, such as at least 100 mbar less than ambient pressure but no more than 800 mbar less than ambient pressure.

The pressure of the vacuum is preferably selected so that the pressure is no more than 1000 mbar less than ambient pressure, such as no more than 900 mbar less than ambient pressure, for example no more than 800 mbar less than ambient pressure, such as no more than 700 mbar less than ambient pressure, for example no more than 600 mbar less than ambient pressure, such as no more than 500 mbar less than ambient pressure.

In one embodiment, the pressure of the vacuum is between less than 1000 mbar and 100 mbar, such as between 950 mbar and 100 mbar, for example between 900 mbar and 100 mbar, such as between 850 mbar and 100 mbar, for example between 800 mbar and 100 mbar, such as between 750 mbar and 100 mbar, for example between 700 mbar and 100 mbar, such as between 650 mbar and 100 mbar, for example between 600 mbar and 100 mbar, such as between 550 mbar and 100 mbar, for example between 500 mbar and 100 mbar, such as between 450 mbar and 100 mbar, for example between 400 mbar and 100 mbar, such as between 350 mbar and 100 mbar, for example between 300 mbar and 100 mbar, such as between 250 mbar and 100 mbar, for example between 200 mbar and 100 mbar.

In one embodiment, the pressure of the vacuum is between less than 1000 mbar and 200 mbar, such as between 1000 mbar and 250 mbar, for example between 1000 mbar and 300 mbar, such as between 1000 mbar and 350 mbar, for example between 1000 mbar and 400 mbar, such as between 1000 mbar and 450 mbar, for example between 1000 mbar and 500 mbar, such as between 1000 mbar and 550 mbar, for example between 1000 mbar and 600 mbar, such as between 1000 mbar and 650 mbar, for example between 1000 mbar and 700 mbar, such as between 1000 mbar and 750 mbar, for example between 1000 mbar and 800 mbar, such as between 1000 mbar and 850 mbar, for example between 1000 mbar and 900 mbar, such as between 1000 mbar and 950 mbar.

In a preferred embodiment, the pressure of the vacuum is between about 900 mbar and 500 mbar.

The expansion rate depends on the vacuum pump and the size of the vacuum chamber, i.e. how fast pressure in the chamber can be decreased to the desired level. The low vacuum levels according to the present disclosure are achieved almost instantaneously, thus expansion of the paste occurs essentially instantaneously after starting the vacuum pump.

Vacuum expansion is usually performed at a temperature above the freezing point of the paste. In one embodiment, vacuum expansion is performed at ambient temperature or at temperatures below ambient temperature, such as at temperatures of about 0° C. to about 25° C., such as at about 2° C. to about 20° C., for example about 2° C. to about 15° C., such as at about 2° C. to about 10° C., such as about 4° C. to about 20° C., for example about 4° C. to about 15° C., such as at about 4° C. to about 10° C. When the paste comprises sensitive bioactive agents, such as thrombin, vacuum expansion is preferably performed at temperatures below ambient temperatures.

When the paste has been expanded to a desired degree, the paste is frozen by subjecting the paste to a temperature below the freezing point of the paste and/or the glass transition temperature of the paste for a period of time sufficient for the paste to freeze. Freezing occurs without releasing the vacuum and freezing of the paste thus locks the expanded paste structure in place. Thus, further changes in pressure hereafter will not affect the volume of the frozen paste. The freezing step is preferably performed in a freeze-dryer.

The freezing point of the paste and/or the glass transition temperature of the paste can be determined by the skilled person. The desired temperature of the frozen paste is approximately 5° C. less than the lowest of the freezing point of the paste and the glass transition temperature. E.g. if the freezing point of a paste is −35° C., the paste should be cooled to about −40° C.

Drying the Paste

According to the presently disclosed method, the paste is dried to obtain the dry composition. The paste may be dried by any suitable methods known to a person of skill.

In a preferred embodiment, the paste is freeze-dried. Any suitable freeze-drying technique and equipment known to the person of skill may be used.

When freeze-drying is used to prepare the dry composition, expansion, freezing and drying can advantageously be performed as a continuous process in a single apparatus.

A further advantage of freeze-drying is that it allows for retention of a vacuum inside the container holding the dry composition, which plays a role in the reconstitution of the dry composition.

Freeze-drying (also known as lyophilisation and cryodesiccation) is a dehydration process typically used to preserve a perishable material or make the material more convenient for transport. Freeze-drying works by freezing the material and then reducing the surrounding pressure to allow the frozen water in the material to sublimate directly from the solid phase to the gas phase.

There are essentially three categories of freeze-dryers: the manifold freeze-dryer, the rotary freeze-dryer and the tray style freeze-dryer. Two components are common to all types of freeze-dryers: a vacuum pump to reduce the ambient gas pressure in a vessel containing the substance to be dried and a condenser to remove the moisture by condensation on a surface cooled to −40 to −80° C. The manifold, rotary and tray type freeze-dryers differ in the method by which the dried substance is interfaced with a condenser. In manifold freeze-dryers a short usually circular tube is used to connect multiple containers with the dried product to a condenser. The rotary and tray freeze-dryers have a single large reservoir for the dried substance.

Rotary freeze-dryers are usually used for drying pellets, cubes and other pourable substances. The rotary dryers have a cylindrical reservoir that is rotated during drying to achieve a more uniform drying throughout the substance. Tray style freeze-dryers usually have rectangular reservoir with shelves on which products, such as pharmaceutical solutions and tissue extracts, can be placed in trays, vials and other containers.

Manifold freeze-dryers are usually used in a laboratory setting when drying liquid substances in small containers and when the product will be used in a short period of time. A manifold dryer will dry the product to less than 5% moisture content. Without heat, only primary drying (removal of the unbound water) can be achieved. A heater must be added for secondary drying, which will remove the bound water and will produce a lower moisture content.

Tray style freeze-dryers are typically larger than the manifold dryers and are more sophisticated. Tray style freeze-dryers are used to dry a variety of materials. A tray freeze-dryer is used to produce the driest product for long-term storage. A tray freeze-dryer allows the product to be frozen in place and performs both primary (unbound water removal) and secondary (bound water removal) freeze-drying, thus producing the dryest possible end-product. Tray freeze-dryers can dry products in bulk or in vials or other containers. When drying in vials, the freeze-drier is supplied with a stoppering mechanism that allows a stopper to be pressed into place, sealing the vial before it is exposed to the atmosphere. This is used for long-term storage, such as vaccines.

Improved freeze drying techniques are being developed to extend the range of products that can be freeze dried, to improve the quality of the product, and to produce the product faster with less labor.

Ever since the 1930s, industrial freeze drying has been dependent on a single type of equipment: the tray freeze drier. In 2005 a quicker and less-labor intensive freeze drying method was developed for bulk materials. This freeze drying process proved to be able to produce free-flowing powder from a single vessel. Known as [Active Freeze Drying] AFD technology, the new process used continuous motion to improve mass transfer and hence cutting processing time, while also eliminating the need to transfer to and from drying trays and downstream size reduction devices.

There are four stages in the complete freeze-drying process: pretreatment, freezing, primary drying, and secondary drying.

Pretreatment includes any method of treating the product prior to freezing. This may include concentrating the product, formulation revision (i.e., addition of components to increase stability and/or improve processing), decreasing a high vapor pressure solvent or increasing the surface area. In many instances the decision to pretreat a product is based on theoretical knowledge of freeze-drying and its requirements, or is demanded by cycle time or product quality considerations. Methods of pretreatment include: Freeze concentration, Solution phase concentration, Formulation to Preserve Product Appearance, Formulation to Stabilize Reactive Products, Formulation to Increase the Surface Area, and Decreasing High Vapor Pressure Solvents.

In a lab, freezing is often done by placing the material in a freeze-drying flask and rotating the flask in a bath, called a shell freezer, which is cooled by mechanical refrigeration, dry ice and methanol, or liquid nitrogen. On a larger scale, freezing is usually done using a freeze-drying machine. In this step, it is important to cool the material below its triple point, the lowest temperature at which the solid and liquid phases of the material can coexist. This ensures that sublimation rather than melting will occur in the following steps. Larger crystals are easier to freeze-dry. To produce larger crystals, the product should be frozen slowly or can be cycled up and down in temperature. This cycling process is called annealing. In other cases it is better that the freezing is done rapidly, in order to lower the material to below its eutectic point quickly, thus avoiding the formation of ice crystals. Usually, the freezing temperatures are between −40° C. and −80° C. The freezing phase is the most critical in the whole freeze-drying process, because the product can be spoiled if badly done.

Amorphous materials do not have a eutectic point, but they do have a critical point, below which the product must be maintained to prevent melt-back or collapse during primary and secondary drying.

During the primary drying phase, the pressure is lowered (to the range of a few millibars or less), and enough heat is supplied to the material for the water to sublime.

The amount of heat necessary can be calculated using the sublimating molecules' latent heat of sublimation. In this initial drying phase, about 95% of the water in the material is sublimated. This phase may be slow (can be several days in the industry), because, if too much heat is added, the material's structure could be altered.

In this phase, pressure is controlled through the application of a medium vacuum. The vacuum speeds sublimation, making it useful as a deliberate drying process. Furthermore, a cold condenser chamber and/or condenser plates provide a surface(s) for the water vapour to re-solidify on. This condenser plays no role in keeping the material frozen; rather, it prevents water vapor from reaching the vacuum pump, which could degrade the pump's performance. Condenser temperatures are typically below −50° C.

It is important to note that, in this range of pressure, the heat is brought mainly by conduction or radiation; the convection effect is negligible, due to the low air density.

The vapour pressure of water is the pressure at which water vapour is saturated. At higher pressures water would condense. The water vapour pressure is the partial pressure of water vapour in any gas mixture saturated with water. The water vapour pressure determines the temperature and pressure necessary for freeze-drying to occur. Vapour pressure of water (mTorr=millitorr; mB=millibar) is shown in the below table:

Temp (C.) mTorr mB 0 4579 6.104 −4 3280 4.372 −8 2326 3.097 −12 1632 2.172 −16 1132 1.506 −20 930 1.032 −24 526 0.6985 −28 351 0.4669 −32 231 0.3079 −36 150 0.2020 −40 96.6 0.1238 −44 60.9 0.0809 −48 37.8 0.0502 −52 23.0 0.0300 −56 13.8 0.0183 −60 8.0 0.0107 −64 4.6 0.0061 −68 2.6 0.0034 −72 1.4 0.0018

The secondary drying phase aims to remove unfrozen water molecules, since the ice was removed in the primary drying phase. This part of the freeze-drying process is governed by the material's adsorption isotherms. In this phase, the temperature is raised higher than in the primary drying phase, and can even be above 0° C., to break any physico-chemical interactions that have formed between the water molecules and the frozen material. Usually the pressure is also lowered in this stage to encourage desorption (typically in the range of microbars). However, there are products that benefit from increased pressure as well.

After the freeze-drying process is complete, the vacuum may be broken with an inert gas, such as nitrogen, before the material is sealed.

In one embodiment, the vacuum is retained in the product chamber to allow for easy addition of liquid for reconstitution.

At the end of the operation, the final residual water content in the freeze-dried product is in general very low, such as around 2% or lower.

The freeze-drying process transforms the paste into a “cake-like” dry composition, which upon addition of an adequate amount of an aqueous medium, such as water, will form a ready-to use paste spontaneously, i.e. no mechanical mixing/reconstitution is required for said paste to form.

In an alternative embodiment of the present disclosure involving vacuum expansion of the paste prior to drying, the expanded paste is not frozen prior to drying of the paste. Neither is the paste dried by freeze-drying. Rather the low vacuum is upheld while the paste is dried by subjecting the expanded paste to an increased temperature until the paste is dry. The increased temperature is typically in the range of about 30-200° C., such as about 50° C. to about 150° C.

Outer Packaging

In one embodiment the dry composition contained within e.g. a medical delivery device, such as the herein disclosed syringe, or other containment unit, is further contained within an outer packaging so that the product is kept sterile until use. This will allow the user to remove the outer packaging and transfer the haemostatic composition into a sterile field.

The outer packaging is usually made from a flexible, semi-rigid or rigid material and typically consists of materials such as plastic, aluminium foil and/or plastic laminate, where the plastic may be selected from the group consisting of PET, PETG, PE, LLDPE, CPP, PA, PETP, METPET, Tyvek and optionally bonded with an adhesive, such as polyurethane, or co-extruded.

In one embodiment, the outer packaging is an aluminium foil outer packaging. The outer packaging preferably forms a complete barrier to moisture.

The outer packaging is preferably able to endure sterilisation treatment such as by radiation.

Sterilisation

The dry composition of the present disclosure is preferably sterile. This can be by aseptic production or by any suitable sterilisation technique known in the art. The sterilisation preferably occurs after the packaging step, i.e. when the dry composition is contained within an outer packaging. Thus, in a preferred embodiment sterilisation is terminal sterilisation.

Sterilisation refers to any process that effectively kills or eliminates transmissible agents (such as fungi, bacteria, viruses, prions and spore forms etc.). Sterilisation of the dry composition can be achieved through e.g. application of heat, chemicals, and irradiation. Heat sterilization include autoclaving (uses steam at high temperatures) and dry heat; radiation sterilisation include X-rays, gamma and beta rays, UV light and subatomic particles; chemical sterilisation include using ethylene oxide gas, ozone, chlorine bleach, glutaraldehyde, formaldehyde, ortho phthalaldehyde, hydrogen peroxide and peracetic acid.

In one embodiment, the dry composition is sterilised by irradiation, e.g. ionizing irradiation, so as to provide sterility to the composition. Such irradiation may include e-beam (beta irradiation) or gamma irradiation. The level of irradiation and conditions for sterilisation, including the time that the composition is irradiated, are those that provide sterile compositions. Sterilisation conditions are similar to those currently utilized in the preparation of haemostatic loose powders currently available. Once having the benefit of this disclosure, one skilled in the art will be able to readily determine the level of irradiation necessary to provide sterile compositions.

When thrombin or other sensitive bioactive agents are present in the dried product, sterilisation is usually performed as terminal sterilisation with about 25 kGy or less of beta or gamma irradiation.

In one embodiment, sterilisation is performed with ethylene oxide.

Sterilisation with dry heat may typically be carried out by heating the dry haemostatic composition to a temperature between 100° C. and 250° C., such as about 110° C. to about 200° C. In particular the temperature may be in the range of 110-160° C., e.g. in the range of 110-140° C., or in the range of 120-180° C., or in the range of 130-170° C., or in the range of 130-160° C., or in the range of 120-150° C. Heat sterilisation is usually not utilised when the dry composition contains thrombin, since heat treatment would inactivate the thrombin.

In one embodiment, the dry haemostatic composition is not sterilised after packaging.

When the dry haemostatic composition is manufactured by aseptic production techniques, the product is already sterile when placed in the outer packaging and no further sterilisation is required. Thus, in one embodiment the present disclosure relates to a composition produced by aseptic techniques.

Reconstitution

The present inventors have found that a dry composition prepared by the presently disclosed methods efficiently reconstitutes to form a flowable paste having a soft consistency suitable for use in haemostatic and wound healing procedures. The dry composition reconstitutes spontaneously, i.e. without any mechanical mixing required.

The dry composition is reconstituted by adding a suitable aqueous medium. The aqueous medium may be added by any suitable mechanism. Preferably, the aqueous medium is sterile and compatible with surgical use.

The aqueous medium is added in an amount sufficient to obtain a wet paste having a desired content of the biocompatible polymer. In one embodiment, the volume of liquid added to the dry composition corresponds essentially to the volume of liquid which was removed by the drying procedure. In case a thinner paste composition is desired, more liquid can be added to the dried paste than was initially removed by the drying procedure.

Preferably, the paste is reconstituted by adding an amount of liquid to a container, such as a medical delivery device, having the dried paste composition disposed therein, even more preferred to the same container which held the paste during drying.

In one embodiment, the dry composition is reconstituted by attaching a second container holding an amount of an aqueous medium to the first container holding the dry composition.

Preferably, the container comprising the reconstitution liquid is essentially free from air or another gas. The advantage of this is that reconstitution is independent of how the containers are oriented in space in relation to each other.

In one embodiment, there is a vacuum inside the product chamber of the first container, i.e. the pressure inside the product chamber of the first container is less than that of the surroundings, i.e. less than atmospheric pressure.

In one embodiment, the pressure in the second container is greater than the pressure in the first container, the pressure difference allowing for automatic liquid flow from the second container to the first container. This can e.g. be achieved by the first container having a pressure below atmospheric pressure, while the pressure inside the second container is about atmospheric pressure. Thus, upon opening a valve separating the two containers, the aqueous medium is automatically drawn into the product chamber of the first container due to the pressure difference. The result is a reconstituted paste, see e.g. FIGS. 12-13.

Thus, in one embodiment, the present disclosure relates to a method for reconstituting a dry composition comprising the steps of:

-   -   a) providing a first container comprising a product chamber         containing a dry paste composition and a valve, preferably         wherein the pressure within the product chamber is less than the         surrounding atmospheric pressure,     -   b) providing a second container comprising an aqueous medium,         preferably wherein the pressure within the second container is         greater than the pressure within the product chamber of the         first container,     -   c) connecting the first container and the second container using         suitable connecting means, and     -   d) opening the valve.

In one embodiment, the second container is a collapsible container such as a plastic bag. Upon attachment to the first container and opening of the valve, the bag collapses due to the pressure difference, thus allowing for liquid flow from the bag to the product chamber and reconstitution of the paste as illustrated in FIGS. 12-13.

In another embodiment, the second container is a non-collapsible container comprising a plunger, such as a rigid- or semi-rigid plastic container. Upon attachment to the first container and opening of the valve the plunger allows for liquid flow from the aqueous medium container to the product chamber and reconstitution of the paste without exerting manual pressure upon the plunger as illustrated in FIGS. 12-13.

In one embodiment a ready-to-use paste forms spontaneously upon addition of liquid to the dry composition disposed within the container within less than about 30 seconds, preferably within less than about 20 seconds, more preferred within less than about 10 seconds, even more preferred within less than about 5 seconds, such as less than about 3 seconds, for example less than about 2 seconds. The reconstituted paste usually requires no further mixing or other forms of manipulations before use. Thus, when the dry composition is present in a medical delivery device, such as a syringe, it can be applied directly to a patient immediately after liquid addition, e.g. for haemostatic purposes, by extruding the paste from the medical delivery device to a bleeding wound.

In a preferred embodiment, a ready-to-use paste forms within less than about 10 seconds, for example less than about 5 seconds, such as less than about 3 seconds, for example less than about 2 seconds.

After reconstitution, the container, for example a syringe, such as the herein disclosed syringe, may be fitted with an applicator tip suitable for administering the paste in a more precise manner as illustrated in FIG. 14.

In one embodiment the applicator tip is bendable or malleable and will maintain a desired configuration chosen by the user so that it stays at an optimum angle for easy access and exact product placement. Further, it can be cut to a desired length with a pair of nurses dressing scissors or similar type of scissors. These features allow for accurate and convenient application of the paste. In one embodiment the applicator tip is essentially as described in WO 2011/047753.

In one embodiment, the reconstituted paste has a consistency within the range of about 100 g×sec to about 10,000 g×sec, such as from about 500 g×sec to about 5000 g×sec, for example from about 1000 g×sec to about 3000 g×sec, such as from about 1500 g×sec to about 2000 g×sec.

In one embodiment, the reconstituted paste has a consistency of less than about 5000 g×sec, for example less than about 4000 g×sec, such as less than about 3000 g×sec, for example less than about 2000 g×sec.

A Haemostatic Paste

In one embodiment the present disclosure relates to a paste suitable for use in haemostatic procedures. The haemostatic paste may be obtained by the methods disclosed herein. The paste of the present disclosure has a desirable soft and light consistency as compared to pastes currently known in the art.

The haemostatic paste of the present disclosure comprises a biocompatible polymer and preferably has a consistency of less than 5000 g×sec.

The biocompatible polymer is usually in the form of substantially water-insoluble particles. Preferably, it is a cross-linked biocompatible polymer suitable for use in haemostasis and/or wound healing, such as cross-linked gelatine particles as described elsewhere herein.

The paste may be made using any aqueous medium suitable for preparing a paste known to a person of skill as described elsewhere herein.

In one embodiment, the consistency of the paste is less than about 4500 g×sec.

In one embodiment, the consistency of the paste is less than about 4000 g×sec.

In one embodiment, the consistency of the paste is less than about 3500 g×sec.

In one embodiment, the consistency of the paste is less than about 3000 g×sec.

In one embodiment, the consistency of the paste is less than about 2500 g×sec.

In one embodiment, the consistency of the paste is less than about 2000 g×sec.

In one embodiment, the consistency of the paste is within the range of about 100 g×sec to about 5000 g×sec, such as from about 500 g×sec to about 4000 g×sec, for example from about 500 g×sec to about 3500 g×sec, such as from about 500 g×sec to about 3000 g×sec, for example from about 500 g×sec to about 2500 g×sec, such as from about 500 g×sec to about 2000 g×sec.

In one embodiment, the consistency of the paste is within the range of about 1000 g×sec to about 4000 g×sec, for example from about 1000 g×sec to about 3500 g×sec, such as from about 1000 g×sec to about 3000 g×sec, for example from about 1000 g×sec to about 2500 g×sec, such as from about 1000 g×sec to about 2000 g×sec.

The paste of the present disclosure may further comprise one or more hydrophilic compounds as described elsewhere herein. For example, the paste may comprise a polyol as hydrophilic compound, such as a sugar alcohol, at a concentration of at least 1%, more preferred at least 2%, such as at least 3%, for example at least 4%, such as at least 5%. In one embodiment, the sugar alcohol is mannitol.

The paste of the present disclosure may further comprise one or more further compounds and/or bioactive agents and/or extrusion enhancers as described elsewhere herein. Preferably, the paste of the present disclosure comprises thrombin as bioactive agent.

In a specific embodiment, the present disclosure relates to a paste suitable for use in haemostasis comprising:

a) a biocompatible polymer at about 10% to about 40%,

b) an aqueous medium such as water, and optionally one or more of

c) a hydrophilic compound at about 1% to about 20%,

d) a bioactive agent, and

e) an extrusion enhancer,

wherein said paste has a consistency of less than 5000 g×sec.

In one embodiment, the present disclosure relates to a syringe comprising said paste.

Medical Use

The present disclosure further relates to use of the dry composition or the paste disclosed herein for promoting haemostasis and/or wound healing in an individual in need thereof.

The paste of the present disclosure has a soft consistency, which may be preferable in certain types of surgeries. In addition, surgeon preferences also vary with regards to the consistency of the pastes, where some surgeons prefer a softer consistency than others. Consequently, the presently disclosed dry composition and paste may satisfy the need of surgeons having a preference for a softer paste consistency.

The paste of the present disclosure may e.g. be used in an array of surgical procedures wherein bleeding control is desired. Haemostatic products in paste form are able to conform efficiently to irregular surfaces and are therefore useful for providing rapid haemostasis on rough or uneven surfaces where haemostatic sponges are not efficient.

Currently available haemostatic pastes (e.g. Floseal® and Surgiflo®) are usually prepared (i.e. reconstituted) directly at the surgical site at the time of need by the medical practitioner, i.e. the doctors or nurses, by addition of liquid to a container, such as a syringe, containing an amount of a biocompatible polymer. The biocompatible polymer may be pre-wetted with the liquid or be essentially dry (free-flowing powder). The paste is thus often prepared under extremely stressful conditions and it is therefore essential that the process for preparing the paste is simple and fast to ensure that the bleeding is arrested as quickly as possible and that no mistakes are made while preparing the paste such that the nurse can keep focus on the needs of the surgeon instead of on preparing the haemostat. It is also important that the consistency of the paste is suitable for the particular surgical procedure, that the consistency of the product is independent from preparation to preparation, and that the consistency of the reconstituted paste does not very substantially over time (after preparation).

Due to the time-consuming and often intricate preparation steps required for reconstituting the currently available flowable paste products, they are often pre-prepared in the OR before surgery in case they are needed under surgery. Consequently, unused product is thus often discarded because the surgeon does not use as much of the product as expected. Unused product must also be discarded if the time limit for using the reconstituted product is expired. This causes unnecessary high OR costs.

The preparation of the paste of the present disclosure is simple and fast—the dry composition reconstitutes to form a flowable paste within seconds of coming into contact with the aqueous medium. Importantly, no mechanical mixing steps are required. Thus, there is no need for pre-preparing the paste prior to a surgical procedure and OR costs can be kept at a minimum.

As the reconstitution of the dry composition of the present disclosure is independent from mechanical mixing, the consistency of the reconstituted paste will always be the same when the correct amount of liquid is added. This is not always the case with the conventional pastes, where the consistency of the paste may depend on the force applied and time spent mixing. That no mechanical mixing is required also means that less time is spent preparing the paste, which in turn leads to increased patient safety, both due to the fact that the haemostatic paste can be applied to the patient faster and that the simple preparation method decreases the likelihood of mistakes being made during the preparation of the haemostatic paste.

When thrombin is comprised within the dry composition, the invention further has the advantage over conventional pastes in that it avoids the time-consuming and error-prone thrombin dilution and addition steps involved in current methods for preparing flowables.

Another notable advantage of the dry composition of the present invention is that a kit consisting of fewer components can be prepared as compared to e.g. current haemostatic flowable kits. All there is required to prepare a flowable paste composition in the OR is the dry composition as described herein comprised within a medical delivery device and a container comprising an aqueous medium for reconstitution. Upon connection of the two, a ready-to-use flowable paste containing all necessary agents for effective haemostasis including thrombin is formed spontaneously when the aqueous medium is automatically drawn into the medical delivery device containing the dry composition. Thus, no extra syringes, vial adapters, needles and mixing bowls are required with the product prepared according to the methods of the present disclosure. This means that the manufacturing costs can be decreased and also ensures good patient safety, since there are less components for the OR staff to keep track of during surgery. Needle-free preparation of the haemostat also ensures the safety of the OR staff.

In one embodiment the present disclosure relates to a method for arresting bleeding/promoting haemostasis in an individual in need thereof by application of the paste of the present disclosure to a site of bleeding.

The paste of the present disclosure may be used for any type of surgery including general surgery, cardiothoracic surgery, vascular surgery, plastic surgery, paediatric surgery, colorectal surgery, transplant surgery, surgical oncology, trauma surgery, endocrine surgery, breast surgery, skin surgery, otolaryngology, gynaecology, oral and maxillofacial surgery, dental Surgery, orthopaedic surgery, neurosurgery, ophthalmology, podiatric surgery, urology.

In one embodiment the present disclosure relates to a method for promoting wound healing in an individual in need thereof by application of the paste of the present disclosure to a wound.

A “wound” refers broadly to injuries to the skin and/or underlying (subcutaneous) tissue initiated in different ways (e.g., pressure sores from extended bed rest and wounds induced by trauma) and with varying characteristics. Wounds may be classified into one of four grades depending on the depth of the wound: i) Grade I: wounds limited to the epithelium; ii) Grade II: wounds extending into the dermis; iii) Grade III: wounds extending into the subcutaneous tissue; and iv) Grade IV (or full-thickness wounds): wounds wherein bones are exposed (e.g., a bony pressure point such as the greater trochanter or the sacrum). The present disclosure relates to treatment of any type of wound mentioned above using the paste of the present disclosure.

The treatment of a wound can in principle result in healing of the wound or in accelerated healing of the wound. The accelerated healing can be a result of e.g. administration of a wound-healing promoting substance. Alternatively, the wound healing can be promoted by preventing bacterial or viral infection, or by reducing the risk of such an infection which would otherwise have prolonged the wound treatment process.

In one embodiment the present disclosure relates to a method for promoting bone and/or tendon healing in an individual in need thereof by application of the paste of the present disclosure to the injured bone/tendon.

The “individual” referred to herein may be any mammal, including, but not limited to, mammals of the order Rodentia, such as mice and hamsters, and mammals of the order Logomorpha, such as rabbits. It is preferred that the mammals are from the order Carnivora, including Felines (cats) and Canines (dogs). It is more preferred that the mammals are from the order Artiodactyla, including Bovines (cows) and Swines (pigs) or of the order Perssodactyla, including Equines (horses). It is most preferred that the mammals are of the order Primates, Ceboids, or Simoids (monkeys) or of the order Anthropoids (humans and apes). An especially preferred mammal is the human.

In one embodiment the present disclosure relates to the dry composition as disclosed herein, for use in the treatment of a wound, e.g. for arresting bleeding or for promoting wound healing.

A Haemostatic Kit

The present disclosure further relates to a haemostatic kit comprising the dry composition of the present disclosure and an amount of aqueous medium matched to the amount of the dry composition so that upon addition of the aqueous medium, a haemostatic paste of a consistency suitable for use as a haemostatic paste will form without the need for mechanical mixing.

Hence, in one embodiment the present disclosure relates to a haemostatic kit comprising:

-   -   a) a first container comprising the dry composition obtained by         the method of the present disclosure,     -   b) a second container comprising an aqueous medium, and     -   c) optionally an outer packaging.

In a further embodiment the present disclosure relates to a haemostatic kit comprising:

-   -   a) the presently disclosed syringe comprising a dry composition     -   b) a container comprising an aqueous medium, and     -   c) optionally an outer packaging.

The dry composition may be any dry composition, in particular a dry composition that upon addition of the aqueous medium, a haemostatic paste will form of a consistency suitable for use as a haemostatic paste, such as form spontaneously within seconds, such as a dry composition obtained by the method of the present disclosure.

In one embodiment, the dry composition comprises thrombin.

In one embodiment, the kit further comprises one or more applicator tips.

The kit may optionally contain instructions for use of the kit.

Example 1

Materials

50 g Gelatine powder (milled cross-linked gelatine sponges)

200 ml buffer

x g Polyol

50% Benzalkoniumchloride (BAC)

0.9% Saline solution

Equipment

Freeze dryer: Christ Alpha 1-4 LSC

Mixer: Kenwood, Major KM616

Method

Buffer solution:

Add 2.0 g±0.1 g BAC (50%) to a 250 mL blue cap bottle

Add 98.0 g±0.5 g water to the BAC

Mix for 2 minutes using magnetic stirring—this is the BAC stock solution

Add 10 g±0.5 g BAC stock solution

Add water to the 2000 mL mark

Place a stopper in the flask and turn it upside down a few times

Mix by magnetic stirring for 5±1 minutes

Paste:

Dissolve x g polyol in 200 ml buffer solution under stirring in the mixer. Add 50 g gelatine powder and mix with the dissolved polyol until a homogeneous paste is obtained, approximately 5 minutes.

Freeze-Drying:

The resulting paste was filled into 10 ml single use plastic syringes (5.5 ml per syringe) comprising a lyophilisation bypass channel and placed at −30° C. for minimum 4 h. The frozen paste was transferred to the freeze-dryer and freeze-dried until dry for approximately 15 h. At the end of the drying cycle the shelves of the lyophiliser were collapsed, thereby moving the plunger and closing the lyo bypass channel. The pressure in the lyophiliser chamber was then brought to ambient pressure leaving a vacuum in the product chamber.

Reconstitution:

The dry haemostatic composition was reconstituted by connecting the syringe comprising the dry composition to a collapsible plastic bag containing water (8 ml). No mechanical mixing or stirring was used. The water was added to the dry composition by utilising the vacuum inside the product chamber, and the composition was left untouched until a paste was re-formed. The vacuum inside the product chamber of the syringe causes the water to be automatically drawn into the syringe from the container holding the water.

Results

The different formulations were tested for time to reconstitution, i.e. the time needed for a paste suitable for haemostatic purposes to spontaneously form without mechanical agitation of any sorts.

Pastes comprising different polyols were made, dried and reconstituted according to the directions above. The contents of the pastes are shown in the tables below.

Content wet Content dry Content wet Content dry [g] [g] [W/W %] [W/W %] Gelatine 50.00 50.00 18.52 70.41 Mannitol 20.00 20.00 7.41 28.17 BAC 0.01 0.01 0.00 0.01 H₂0 200 1.00 74.07 1.41 SUM 270.01 71.01 100 100 Content wet Content dry Content wet Content dry [g] [g] [%] [%] Gelatine 50.00 50.00 18.52 70.41 Xylitol 20.00 20.00 7.41 28.17 BAC 0.01 0.01 0.00 0.01 H₂0 200 1.00 74.07 1.41 SUM 270.01 71.01 100 100 Content wet Content dry Content wet Content dry [g] [g] [%] [%] Gelatine 50.00 50.00 18.52 70.41 Trehalose 20.00 20.00 7.41 28.17 BAC 0.01 0.01 0.00 0.01 H₂0 200 1.00 74.07 1.41 SUM 270.01 71.01 100 100 Content wet Content dry Content wet Content dry [g] [g] [%] [%] Gelatine 50.00 50.00 18.52 70.41 Maltitol 20.00 20.00 7.41 28.17 BAC 0.01 0.01 0.00 0.01 H₂0 200 1.00 74.07 1.41 SUM 270.01 71.01 100 100 Content wet Content dry Content wet Content dry [g] [g] [%] [%] Gelatine 50.00 50.00 18.52 70.41 Sorbitol 20.00 20.00 7.41 28.17 BAC 0.01 0.01 0.00 0.01 H₂0 200 1.00 74.07 1.41 SUM 270.01 71.01 100 100

The polyol:gelatine ratio in the dry compositions was approximately 0.4:1.

The spontaneous reconstitution time of the pastes comprising different polyols made according to the tables above is shown in the table below and in FIG. 1. The experiments were repeated 5 times for each polyol.

Mannitol Xylitol Trehalose Maltitol Sorbitol 1 7 14 11 14 29 2 9 31 28 14 28 3 9 20 16 23 29 4 10 30 29 16 35 5 9 31 23 22 32 Average 8.8 25.2 21.4 17.8 30.6 reconstitution time [sec] Std 1.1 7.8 7.8 4.4 2.9

The experiment shows that different kinds of polyols can be used for making a freeze-dried gelatine paste that will reconstitute spontaneously upon addition of an aqueous medium within less than about 30 seconds. The reconstituted paste has a consistency suitable for direct use as a haemostatic paste.

Example 2. Thrombin

Thrombin was included in the below paste formulation at a theoretical concentration of 2500 IU/product. The paste was made at room temperature (about 20° C.) and mixed as described in Example 1.

The dried paste had a spontaneous reconstitution time of about 5 seconds. The contents of the paste formulation are specified in the table below in the paste (wet) and the dried composition (dry) respectively.

Paste Content wet Content dry Content wet Content dry Formulation [g] [g] [%] [%] Gelatine 50.00 50.00 18.18 56.65 Mannitol 20.00 20.00 7.27 22.66 Glycerol 12.30 12.30 4.47 13.94 (buffer) Glycerol 5.00 5.00 1.82 5.67 (added) BAC 0.01 0.01 0.00 0.01 NaCl 0.01 0.01 0.00 0.01 H₂0 187.68 0.94 68.25 1.06 SUM 275.00 88.26 100 100

The total polyol concentration, i.e. mannitol and glycerol, in the paste was 13.56% and after drying 42.27%.

The polyol:gelatine ratio in the dry composition was approximately 0.75:1.

The paste was dried by freeze-drying and reconstituted as described in Example 1.

The thrombin activity was measured in the reconstituted paste. The results are shown in the table below.

Thrombin Activity - Freeze-dried composition in syringe [IU/product] 2519.60 2884.94 2796.71 Mean activity: 2733.75

No loss of thrombin activity was measured in the reconstituted paste.

The results show that it is not strictly necessary to perform the mixing of the paste at low temperatures to avoid loss of thrombin activity as no decrease in thrombin activity was found when mixing was performed at ambient temperatures.

Example 3. Vacuum Expansion of Pastes Prior to Freeze-Drying

Gelatine pastes comprising mannitol were prepared essentially as described in Example 1 and aliquoted into 10 ml single-use syringes, each syringe receiving 4 g of the paste. The contents of the paste formulation are specified in the table below in the paste (wet) and the dried composition (dry) respectively.

Content wet Content dry Content wet Content dry [g] [g] [W/W %] [W/W %] Gelatine 50.00 50.00 18.52 70.41 Mannitol 20.00 20.00 7.41 28.17 BAC 0.01 0.01 0.00 0.01 H₂0 200 1.00 74.07 1.41 SUM 270.01 71.01 100 100

The prepared pastes were either freeze dried directly as described in Example 1 (standard lyophilisation) or subjected to a low vacuum of about 850 mbar, followed by a freezing step to −40° C. without releasing the vacuum and finally freeze dried essentially as described in Example 1 (vacuum expanded lyophilisation). Vacuum expansion was performed at ambient temperature, i.e. about 20° C. Upon exposure of the pastes to the decreased pressure, i.e. vacuum, the pastes expanded in volume almost instantaneously.

Before vacuum expansion, the density of the gelatine paste was approximately about 0.7 g/ml. After vacuum expansion, the density of the paste was approximately about 0.5 g/ml corresponding to a decrease in the density of the paste by about a factor 0.72 and a concurrent increase in the volume of the paste by about a factor 1.4.

The lyophilised products were reconstituted essentially as described in Example 1 by adding 5.5 ml saline to the lyophilised product and the amount of time for the paste to fully absorb the saline was measured. The vacuum inside the product chamber of the syringes automatically draws in the liquid. Both vacuum expanded and standard pastes were soft and moist after reconstitution and exhibited comparable absorption capacities. The consistency of the reconstituted pastes was considered suitable for use on a patient. The reconstituted pastes had a slightly off white/yellowish colour.

The reconstitution time for the dried paste compositions is shown in the below table and in FIG. 2. The experiments were repeated 5 times (n=5).

Standard Vacuum expanded n lyophilization lyophilization 1 7 1 2 9 2 3 9 1 4 10 1 5 9 1 Average 8.8 1.2 reconstitution time [sec] Std 1.1 0.4

The inventors surprisingly found that by subjecting the paste to vacuum prior to freezing, the haemostatic dried paste reconstituted more than seven times faster than pastes that had not been vacuum expanded. Reconstitution required no mechanical agitation, mixing or stirring of any kind and a ready-to-use haemostatic paste of a consistency suitable for direct use in haemostatic procedures was formed within seconds.

Example 4. Density of Dry Vacuum Expanded Paste

Gelatine pastes comprising mannitol were prepared as described in Examples 1 and 3. The pastes were vacuum expanded using different vacuum levels (1000 mbar (no vacuum), 850 mbar and 600 mbar) and then frozen and freeze-dried as described in Example 3.

The density of the dry paste compositions is shown in the below table and in FIG. 15.

Pressure Ø H Mass Volume Density [mbar] [cm] [cm] [g] [cm³] [g/cm³] 1000 1.4 4.9 1.3 30.2 0.043 850 1.5 5.5 1.4 38.9 0.035 600 1.8 6.0 1.4 61.1 0.023

The dry compositions reconstituted spontaneously to form soft and moist pastes suitable for haemostatic and/or wound healing use.

The results show that different pressures may be used to expand the paste prior to drying.

The results further show that the pressure used for expansion affects the density of the dry paste composition. Indeed, there seems to be a good correlation between the pressure and the density of the dry composition with lower pressures resulting in lower densities of the final dry paste composition.

Example 5. Effect of Vacuum Expansion and Polyol Concentration

Gelatine pastes comprising different amounts of mannitol (no mannitol, medium mannitol (approx. 3.9%) or high mannitol (approx. 7.4%)) were prepared essentially as described in Example 1 with the exception that a Virtis Genesis 35 freeze-dryer was used. Portions of paste were aliquoted into 10 ml single-use syringes having vacumm bypass, each syringe receiving 4 g of the paste. The contents of the paste formulation are specified in the table below in the paste (wet) and the dried composition (dry) respectively.

No Content wet Content dry Content wet Content dry Mannitol [g] [g] [W/W %] [W/W %] Gelatine 50.00 50.00 20.00 98.02 Mannitol 0.00 0.00 0.00 0.00 BAC 0.01 0.01 0.00 0.02 H₂0 200.00 1.00 80.00 1.96 SUM 250.01 51.01 100.00 100.00

Medium Content wet Content dry Content wet Content dry Mannitol [g] [g] [W/W %] [W/W %] Gelatine 50.00 50.00 19.23 81.95 Mannitol 10.00 10.00 3.85 16.39 BAC 0.01 0.01 0.00 0.02 H₂0 200.00 1.00 76.92 1.64 SUM 260.01 61.01 100.00 100.00

High Content wet Content dry Content wet Content dry Mannitol [g] [g] [W/W %] [W/W %] Gelatine 50.00 50.00 18.52 70.41 Mannitol 20.00 20.00 7.41 28.17 BAC 0.01 0.01 0.00 0.01 H₂0 200.00 1.00 74.07 1.41 SUM 270.01 71.01 100.00 100.00

The prepared pastes were either freeze dried directly as described in Example 1 (no expansion) or vacuum expanded by exposure to a low vacuum of about 850 mbar, followed by a freezing step to −40° C. without releasing the vacuum and finally freeze dried essentially as described in Example 1 (vacuum expansion). Vacuum expansion was performed at ambient temperature, i.e. about 20° C.

The lyophilised products were reconstituted by adding 5.5 ml saline to the lyophilised product in the syringe and the amount of time for the paste to fully absorb the saline was measured. No mechanical mixing was performed. The reconstituted pastes were soft and moist and exhibited comparable absorption capacities. However, the consistency of the non-expanded gelatine pastes without mannitol were inferior to pastes containing mannitol and/or pastes having been expanded by vacuum. The reconstituted pastes had a slightly off white/yellowish colour.

The average reconstitution time for the dried paste compositions is shown in the below table and in FIG. 21. Each experiment was repeated 5 times (n=5).

Mannitol Average reconstitution concentration time in seconds +/− [wt %] standard deviation No expansion 0  44.8 +/− 14.2* No expansion 3.9  37.2 +/− 14.7 No expansion 7.4 14.3 +/− 9.7 Expansion 0 13.8 +/− 2.7 Expansion 3.9 12.6 +/− 7.2 Expansion 7.4  3.0 +/− 1.4 *The consistency of the reconstituted paste was clearly inferior to pastes containing mannitol and/or pastes having been expanded by vacuum.

Vacuum expansion of the gelatine pastes prior to freeze-drying greatly reduced the reconstitution time of dried gelatine paste compositions both with and without mannitol. In fact, vacuum expansion was able to reduce the spontaneous reconstitution time of the gelatine pastes with about a factor 3 or more. The spontaneous reconstitution time was further improved, i.e. decreased, by inclusion of mannitol in the dry compositions. Mannitol also improved the consistency of the reconstituted pastes.

Gelatine pastes containing 7.4% polyethylene glycol (PEG) were also prepared as above, vacuum expanded and freeze-dried. The contents of the paste formulation are specified in the table below in the paste (wet) and the dried composition (dry) respectively.

Content wet Content dry Content wet Content dry PEG [g] [g] [W/W %] [W/W %] Gelatine 50.00 50.00 18.52 70.41 PEG 20.00 20.00 7.41 28.17 BAC 0.01 0.01 0.00 0.01 H₂0 200.00 1.00 74.07 1.41 SUM 270.01 71.01 100.00 100.00

The average reconstitution time for the dried paste compositions comprising PEG was 8.2+/−2.4 seconds (n=5). Dried vacuum-expanded gelatine pastes containing PEG reconstituted about 1.7 times faster than control (vacuum expanded gelatine paste without any hydrophilic compounds added) and had a superior consistency. The results are shown in FIG. 22.

The inventors have also discovered that the volume of a paste aliquot is generally higher in samples being aliquoted first as opposed to last from a single batch of paste. This is thought to be due to a partial collapse of the paste over time causing undesirable variations in paste density. Such variations in density can lead to undesirable variations in the reconstitution time. Vacuum expansion of the paste prior to drying is believed to be able to reduce or even eliminate such differences in paste density which can occur between the first and the last portions of pastes being aliquoted from a single paste batch.

In conclusion, the results show that vacuum expansion before drying greatly improves the reconstitution rate and is able to provide more consistent results with regards to the reconstitution time. The spontaneous reconstitution rate can be further improved by inclusion of increasing amounts of polyols in the dried paste compositions. In addition, inclusion of hydrophilic compounds, such as polyols, in the dried paste compositions also improved the consistency of the reconstituted pastes.

Example 6. Effect of Polyols and Vacuum Expansion on the Consistency of Sodium Bicarbonate-Containing Reconstituted Pastes

Materials

Paste without Polyol:

50 g Gelatine powder (milled Surgifoam sponges)

200 ml 0.005% BAC w/w in MQ water

1% NaHCO₃(Sigma)

Polyol Containing Paste:

50 g Gelatine powder (milled Surgifoam sponges)

200 ml 0.005% BAC w/w in MQ water

20 g D-Mannitol (Sigma)

1% NaHCO3 (Sigma)

A 2.5% citric acid solution was used for reconstituting the dried paste compositions. The pH of the solution was approximately 2.

Equipment

Freeze dryer: Genesis 35

Mixer: Kenwood, Major KM616

Texture analyser: TA.XT.plus, Stable micro systems

Method

Preparing the Pastes

To prepare pastes without polyol, 50 g gelatine powder was placed in a mixing bowl and 200 ml 0.005% BAC w/w in MQ solution was added and stirred until a homogeneous paste was obtained (approximately 10 minutes of mixing in the Kenwood mixer). The resulting paste was weighed and NaHCO₃ added in an amount resulting in a 1% w/w NaHCO₃ containing paste. The NaHCO₃ was mixed into the paste for an additional 2 minutes.

The polyol containing paste was made similarly to the above procedure, except for adding a 200 ml 0.005% BAC w/w in MQ water having 20 g D-Mannitol dissolved in it.

Lyophilisation

The resulting pastes were filled into lyophilisation syringes at 5.5 g portions and the syringes were placed in the lyophiliser. Prior to freezing, a vacuum of app. 450,000 mtorr (about 600 mbar) was applied to a portion of the samples. The portion of samples which were not subjected to vacuum expansion prior to freezing were frozen immediately when placed in the lyophiliser. Thereafter, the samples were frozen to below −40° C. The samples were then dried in the lyophiliser until dry.

Reconstitution

The dried pastes were reconstituted by addition of 7.0 ml of a 2.5% citric acid solution to each syringe. Specifically, the reconstitution liquid was added by connecting the syringe containing the dried paste with another syringe containing the citric acid solution and opening a valve allowing for communication between the two syringes. Due to the reduced pressure within the syringe containing the dried paste, the reconstitution liquid is automatically drawn into the syringe containing the dried paste. All of the samples reconstituted spontaneously without any mechanical mixing required. The spontaneous reconstitution time of the different samples varied according to the table shown in the results section below.

Texture Analysis

The consistency of the reconstituted pastes was tested using a texture analyser (TA.XT.plus, Stable micro systems).

TA Settings

Test mode compression Pre-test speed 5.00 mm/sec Test speed 0.5 mm/sec Post-test speed 10 mm/sec Distance 30.0 mm Trigger type Auto Trigger force 4.0 g Probe P/0.5R ½″ Dia Cylinder Results

The contents of the compositions in wet and dry state were as follows:

1% NaHCO₃, −polyol:

Content wet Content dry Content wet Content dry Excipient [g] [g] [W/W %] [W/W %] Gelatine 50.00 50.00 19.78 93.04 Mannitol 0.00 0.00 0.00 0.00 BAC 0.01 0.01 0.00 0.02 NaHCO₃ 2.73 2.73 1.00 5.08 H₂0 200.00 1.00 79.13 1.86 SUM 252.74 53.74 100.00 100.00 1% NaHCO₃, +polyol (mannitol):

Content wet Content dry Content wet Content dry Excipient [g] [g] [W/W %] [W/W %] Gelatine 50.00 50.00 18.33 67.81 Mannitol 20.00 20.00 7.33 27.12 BAC 0.01 0.01 0.00 0.01 NaHCO₃ 2.73 2.73 1.00 3.70 H₂0 200.00 1.00 73.33 1.36 SUM 272.74 73.74 100.00 100.00

The consistencies were calculated as area under the resulting curve and the results are shown in the below table. Also shown is the average reconstitution time of the samples. All samples reconstituted spontaneously without mechanical mixing although the reconstitution time varied between the groups.

Average consistency Average reconstitution Group (N = 5 for each [g*sec] +/− standard time [sec] +/− standard group) deviation deviation −polyol − vacuum 2120 +/− 557 74 +/− 12 expansion −polyol + vacuum 2237 +/− 449 22 +/− 6  expansion +polyol − vacuum 2411 +/− 641 45 +/− 9  expansion +polyol + vacuum 1725 +/− 463 9 +/− 2 expansion

It was observed that the inclusion of NaHCO₃ resulted in pastes (prior to drying) which on visual inspection seemed to be more dense than pastes prepared without NaHCO₃. This may explain the longer reconstitution times observed as compared to freeze-dried pastes prepared without NaHCO₃, for instance the samples of Example 5 herein.

There is no significant difference in paste consistency between the four tested groups of samples (+/−polyol, +/−vacuum expansion) (P=0.3, Welch's t-test).

Conclusion

The paste consistency was not altered significantly in response to the addition of polyol or in response to the exposure to vacuum expansion. A soft smooth consistency was achieved in all four test conditions, although the reconstitution time varied depending on the inclusion of polyol and the use of vacuum expansion prior to freeze-drying. Upon reconstitution, the NaHCO₃ in the dry compositions reacts with the acid in the reconstitution liquid and CO₂ will form. The CO₂ expands inside the paste, thereby altering the consistency regardless of the presence of polyol or the exposure to vacuum expansion.

Example 7. Effect of Varying the Concentration of Sodium Bicarbonate on the Consistency of Reconstituted Pastes

Materials

NaHCO₃ Containing Paste:

100 g Gelatine powder (milled Surgifoam sponges)

400 ml 0.005% BAC w/w in MQ water

40 g D-Mannitol (Sigma)

x g NaHCO₃(Sigma)

Standard Paste (Control):

50 g Gelatine powder (milled Surgifoam sponges)

200 ml 0.005% BAC w/w in MQ water

20 g D-Mannitol (Sigma)

A 2.5% citric acid solution was used for reconstituting the dried paste compositions. The pH of the solution was about 2.

Equipment

Freeze dryer: Genesis 35

Mixer: Kenwood, Major KM616

Texture analyser: TA.XT.plus, Stable micro systems

Method

Preparing the Pastes

40 g mannitol was completely dissolved in 400 ml 0.005% BAC w/w in MQ solution under stirring. 100 g gelatine powder was added and mixed with the dissolved Mannitol solution until a substantially homogeneous paste was obtained (approximately 10 minutes of mixing in the Kenwood mixer). The resulting paste was divided into two equally sized portions (265.6 g) and x g of NaHCO₃ was added to each portion according to the below table and mixed for an additional 2 minutes.

Formulation x: NaHCO₃ % w/w NaHCO₃ [g] 1% NaHCO₃ 2.73 0.5% NaHCO₃ 1.36 0% NaHCO₃ 0

The standard paste was prepared in a similar manner except for adding the NaHCO₃ and the final mixing step.

Lyophilisation

The resulting pastes were filled into lyophilisation syringes at 5.5 g portions and the syringes were placed in the lyophiliser. Prior to freezing, a vacuum of app. 450,000 mtorr (about 600 mbar, i.e. about 400 mbar less than ambient pressure) was applied to the samples. Thereafter, the samples were frozen to below −40° C. The samples were then dried in the lyophiliser until dry.

Reconstitution

The dried pastes were reconstituted by addition of 7.0 ml of a 2.5% citric acid solution. Specifically, the reconstitution liquid was added by connecting the syringe containing the dried paste with another syringe containing the citric acid solution and opening a valve allowing for communication between the two syringes. Due to the reduced pressure within the syringe containing the dried paste, the reconstitution liquid is automatically drawn into the syringe containing the dried paste. The dried pastes reconstituted spontaneously within less than 10 seconds without any mechanical mixing required.

Texture Analysis

The consistency of the different formulations was tested using a texture analyser (TA.XT.plus, Stable micro systems). TA settings were as indicated for Example 6.

Results

The contents of the compositions in wet and dry state were as follows:

0% NaHCO₃ in Wet Paste Prior to Drying:

Content wet Content dry Content wet Content dry Excipient [g] [g] [W/W %] [W/W %] Gelatine 50.00 50.00 18.52 70.41 Mannitol 20.00 20.00 7.41 28.17 BAC 0.01 0.01 0.00 0.01 H₂0 200.00 1.00 74.07 1.41 SUM 270.01 71.01 100.00 100.00 0.5% NaHCO₃ in Wet Paste Prior to Drying:

Content wet Content dry Content wet Content dry Excipient [g] [g] [W/W %] [W/W %] Gelatine 50.00 50.00 18.43 67.81 Mannitol 20.00 20.00 7.37 27.12 BAC 0.01 0.01 0.00 0.01 NaHCO₃ 1.36 1.36 0.50 1.88 H₂0 200.00 1.00 73.72 1.38 SUM 271.31 72.31 100.00 100.00 1% NaHCO₃ in Wet Paste Prior to Drying:

Content wet Content dry Content wet Content dry Excipient [g] [g] [W/W %] [W/W %] Gelatine 50.00 50.00 18.33 67.81 Mannitol 20.00 20.00 7.33 27.12 BAC 0.01 0.01 0.00 0.01 NaHCO₃ 2.73 2.73 1.00 3.70 H₂0 200.00 1.00 73.33 1.36 SUM 272.74 73.74 100.00 100.00

The consistencies of the reconstituted pastes were calculated as area under the resulting curve and the results are shown in the below table.

Formulation Area [g × sec] +/− standard deviation 0% NaHCO₃ 5183 +/− 864 0.5% NaHCO₃ 2829 +/− 802 1% NaHCO₃ 1499 +/− 373

The results are also depicted in FIG. 23.

The study shows that the presence of 0.5% sodium bicarbonate in the paste prior to drying (corresponding to about 1.9% in the dry composition), decreases the area under the curve by about 45% while 1% sodium bicarbonate in the paste prior to drying (corresponding to about 3.7% in dry composition), decreases the area under the curve by about 71% compared to control (0% NaHCO₃). The area under the curve is a measure for the consistency or softness of the pastes.

The reconstituted pastes comprising sodium carbonate were visibly whiter than the reconstituted pastes without sodium bicarbonate. The more gas a paste contains, the lighter the colour of the paste will be.

Conclusion

The consistency of the reconstituted pastes softens as the concentration of NaHCO₃ increases. This is presumably due to the CO₂ formed when the base NaHCO₃ reacts with the citric acid upon reconstitution of the dried paste compositions. The CO₂ formed expands inside the paste, thereby altering the consistency of the pastes. A softer, lighter consistency is desirable in some applications of haemostatic pastes.

Example 8. Effect of Incorporating an Acid in the Dry Composition and Reconstituting with a Base

Materials

Paste:

50 g Gelatine powder (milled Surgifoam sponges)

200 ml 0.005% BAC w/w in MQ water

20 g D-Mannitol (Sigma)

1% Tartaric Acid (Sigma)

A 2.5% NaHCO₃ solution was used for reconstituting the dried paste compositions. The pH of the solution was about 8.2.

Equipment

Freeze dryer: Genesis 35

Mixer: Kenwood, Major KM616

Texture analyser: TA.XT.plus, Stable micro systems

Method

Preparing the Paste

To prepare the paste, 50 g gelatine powder was placed in a mixing bowl and 200 ml 0.005% BAC w/w in MQ water having 20 g D-Mannitol dissolved in it was added and stirred until a homogeneous paste was obtained (approximately 10 minutes of mixing in the Kenwood mixer). The resulting paste was weighed and tartaric acid added in an amount resulting in a 1% w/w tartaric acid containing paste. The tartaric acid was mixed into the paste for an additional 2 minutes.

Lyophilisation

The resulting paste was filled into lyophilisation syringes at 5.5 g portions and the syringes were placed in the lyophiliser. Prior to freezing, a vacuum of app. 450,000 mtorr (about 600 mbar) was applied to the samples. Thereafter, the samples were frozen to below −40° C. and dried in the lyophiliser until dry.

Reconstitution

The dried pastes were reconstituted by addition of 7.0 ml of a 2.5% NaHCO₃ solution to each syringe. Specifically, the reconstitution liquid was added by connecting the syringe containing the dried paste with another syringe containing the reconstitution solution and opening a valve allowing for communication between the two syringes. Due to the reduced pressure within the syringe containing the dried paste, the reconstitution liquid is automatically drawn into the syringe containing the dried paste.

Texture Analysis

The consistency of the reconstituted pastes was tested using a texture analyser (TA.XT.plus, Stable micro systems).

TA Settings

Test mode compression Pre-test speed 5.00 mm/sec Test speed 0.5 mm/sec Post-test speed 10 mm/sec Distance 30.0 mm Trigger type Auto Trigger force 4.0 g Probe P/0.5R ½″ Dia Cylinder Results

The contents of the compositions in wet and dry state were as follows:

1% Tartaric Acid

Content wet Content dry Content wet Content dry Excipient [g] [g] [W/W %] [W/W %] Gelatine 50.00 50.00 18.33 67.81 Mannitol 20.00 20.00 7.33 27.12 BAC 0.01 0.01 0.00 0.01 Tartaric acid 2.73 2.73 1.00 3.70 H₂0 200.00 1.00 73.33 1.36 SUM 272.74 73.74 100.00 100.00

The consistency was calculated as area under the resulting curve and the average consistency and reconstitution time are shown in the below table.

Average consistency Average reconstitution [g*sec] +/− standard time [sec] +/− standard deviation deviation +tartaric acid (N = 6) 1864 +/− 579 16 +/− 3

The samples reconstituted spontaneously without any mechanical mixing required.

The consistency of the reconstituted paste achieved by having an acid incorporated into the paste prior to drying and reconstituting with a base was similar to the consistency achieved by having a base incorporated into the paste prior to drying and reconstituting with an acid (see Examples 6 and 7 herein).

Conclusion

A soft smooth consistency was achieved upon reconstitution. Upon reconstitution, the tartaric acid in the dry compositions reacts with the NaHCO₃ in the reconstitution liquid and CO₂ forms. The CO₂ expands inside the paste, thereby altering the consistency of the paste. 

The invention claimed is:
 1. A method for preparing a dry composition comprising: a) providing i) a biocompatible polymer consisting of powder particles which are substantially insoluble in an aqueous medium, ii) an aqueous medium, and iii) either an alkaline compound or an acidic compound, b) mixing the biocompatible polymer, the aqueous medium and the alkaline or acidic compound to obtain a paste, and c) drying the paste, wherein the dry composition comprises at least 0.1% of the alkaline compound or the acidic compound of iii), and wherein if the dry composition comprises an alkaline compound, the alkaline compound is capable of reacting with an acidic compound in an aqueous medium to release a gas and if the dry composition comprises an acidic compound, the acidic compound is capable of reacting with an alkaline compound in an aqueous medium to release a gas, wherein the dry composition is capable of reconstituting to form a substantially homogenous paste without mechanical mixing.
 2. The method according to claim 1, wherein the paste obtained in b) is subjected to i) a reduced pressure, thereby expanding the paste, and ii) the expanded paste is frozen, prior to c).
 3. The method according to claim 1, wherein the paste of a) is further mixed with one or more hydrophilic compounds.
 4. The method according to claim 1, wherein the biocompatible polymer is cross-linked.
 5. The method according to claim 1, wherein the biocompatible polymer comprises or consists of gelatine.
 6. The method according to claim 1, wherein the gas is CO₂.
 7. The method according to claim 1, wherein the alkaline compound is a carbonate salt.
 8. The method according to claim 7, wherein the carbonate salt is sodium bicarbonate (NaHCO₃).
 9. The method according to claim 1, wherein the acidic compound is selected from the group consisting of acetic acid, citric acid, oxalic acid and tartaric acid.
 10. The method according to claim 1, wherein the dry composition comprises from about 0.1% to about 10% of the alkaline compound or the acidic compound.
 11. The method according to claim 1, wherein the drying is freeze-drying.
 12. The method according to claim 1, wherein the dry composition further comprises one or more bioactive agents capable of stimulating haemostasis, wound healing, bone healing, tissue healing and/or tendon healing.
 13. The method according to claim 12, wherein the bioactive agent is thrombin.
 14. The method according to claim 1, wherein the dry composition further comprises an extrusion enhancer.
 15. The method according to claim 1, wherein the paste obtained in b) is transferred into a container suitable for drying of the paste.
 16. The method according to claim 15, wherein the container is a medical delivery device suitable for reconstituting a dry composition and dispensing a paste.
 17. The method according to claim 1, further comprising adding i) an acidic compound in dry form after c) if the dry composition comprises an alkaline compound, or ii) an alkaline compound in dry form after c) if the dry composition comprises an acidic compound, thereby obtaining a dry composition comprising an alkaline compound and an acidic compound.
 18. A method for reconstituting the dry composition obtained by the method of claim 1, further comprising adding an aqueous medium to the dry, wherein the aqueous medium comprises: i) an acidic compound if the dry composition comprises an alkaline compound, ii) an alkaline compound if the dry composition comprises an acidic compound, or iii) neither an acidic nor an alkaline compound if the dry composition comprises both an alkaline and an acidic compound, wherein the acidic compound and the alkaline compound react to release a gas in the presence of said aqueous medium.
 19. A haemostatic kit comprising: a) a first container comprising the dry composition obtained by the method of claim 1, b) a second container comprising an aqueous medium comprising i) an acidic compound if the dry composition comprises an alkaline compound, ii) an alkaline compound if the dry composition comprises an acidic compound, or iii) neither an acidic nor an alkaline compound if the dry composition comprises both an alkaline and an acidic compound, and c) optionally an outer packaging. 